CN114784401A - Long-cycle-life lithium ion battery and method for prolonging cycle life of lithium ion battery - Google Patents

Long-cycle-life lithium ion battery and method for prolonging cycle life of lithium ion battery Download PDF

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CN114784401A
CN114784401A CN202210560328.3A CN202210560328A CN114784401A CN 114784401 A CN114784401 A CN 114784401A CN 202210560328 A CN202210560328 A CN 202210560328A CN 114784401 A CN114784401 A CN 114784401A
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lithium
battery
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郭玉国
赵玉明
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Institute of Chemistry CAS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H01M10/448—End of discharge regulating measures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4271—Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing

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Abstract

The invention relates to a long-cycle-life lithium ion battery, which comprises a positive electrode, a negative electrode, a diaphragm, electrolyte, a battery shell, a lug and a battery management system, wherein the negative electrode is made of graphite, a lithium storage agent, a conductive agent, a binder and a current collector, and the lithium storage agent is a high-capacity alloy negative electrode material; the discharge cut-off voltage is controlled by a battery management system, and when the battery capacity is attenuated to a set value, the discharge cut-off voltage of the lithium ion battery is automatically reduced. The invention controls the discharge cut-off voltage of the battery in stages, controls the active lithium in the lithium storage agent to be released in stages, supplements the lithium consumed in the battery circulation process in time, and obviously prolongs the cycle life of the lithium ion battery; the method is convenient, simple, effective and strong in operability for prolonging the cycle life of the lithium ion battery.

Description

Long-cycle-life lithium ion battery and method for prolonging cycle life of lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a long-cycle-life lithium ion battery and a method for prolonging the cycle life of the lithium ion battery.
Background
The lithium ion battery has the advantages of high energy density, long cycle life, small self-discharge, rapid charge and discharge, good safety and the like, is rapidly developed since the commercialization was realized in 1991, and is widely applied to the fields of various digital products, electronic equipment, electric vehicles, energy storage and the like. The lithium ion battery realizes reversible charge and discharge mainly through reversible shuttling of lithium ions between a positive electrode and a negative electrode, the lithium ions are separated from a positive electrode active material during charging and are inserted into the negative electrode through electrolyte migration, and the opposite is realized during discharging.
The cycle life is an important index for evaluating the performance of the lithium ion battery, and since the commercialization of the lithium ion battery, the cycle life of the lithium ion battery is greatly improved through the improvement of battery materials and battery technology. For practical application, the longer the cycle life of the lithium ion battery, the better, especially for some special fields, the longer the cycle life of the lithium ion battery is required to reduce the use cost, for example, applying the lithium ion battery to large-scale energy storage has great significance for constructing a smart grid, improving the energy utilization efficiency, realizing low-carbon economy and the like, but the lithium ion battery for energy storage generally requires that the cycle number is more than 3500, the service life is more than 10 years, and higher requirements are put forward on the lithium ion battery technology.
In actual use, a lithium ion battery is mainly subjected to charge and discharge cycles by controlling a charge cut-off voltage/cut-off current and a discharge cut-off voltage, active lithium in the battery is continuously consumed with the increase of the number of cycles, and the capacity of the battery is continuously reduced, so that the service life of the lithium ion battery is considered to be finished when the capacity of the lithium ion battery is reduced to 80% of the initial capacity of the lithium ion battery. In order to improve the cycle life of the lithium ion battery, patent CN201610796029.4 provides a method for adding a supplementary active lithium material (LiCoO) to a lithium iron phosphate positive electrode2) To extend the cycle life of a lithium ion battery, but the method needs to be firstWhen the lithium ion battery is charged for the second time, the voltage is charged to 4.45-4.8V, which is far higher than the charge cut-off voltage (3.7-4.0V) of the lithium iron phosphate anode, so that the structure of the lithium iron phosphate anode is possibly damaged, and in addition, the structure of the supplementary active lithium material collapses when the lithium iron phosphate anode is charged for the first time, so that lithium can not be supplemented in subsequent cycles, and the two reasons can limit the degree of prolonging the cycle life of the lithium ion battery. CN202210046115.9 provides a graphite cathode material, is through the graphite granule of two kinds of particle diameters, and the second particle diameter granule specific surface area is big, and the hole is many, can store more electrolyte, and then promotes graphite cathode material's long cycle performance. CN202111349454.6 provides a long cycle life lithium iron phosphate battery, which optimizes the design of battery core by optimizing electrolyte and negative electrode material, and adopts different electrolytes of primary and secondary injection to reduce internal resistance and achieve a longer cycle life.
However, the above prior art is limited in that the improvement of the materials is basically performed to improve the cycle life of the battery, but the method is not easy to be developed in the commercialized battery, and it is more convenient to be industrialized if the cycle life of the battery can be improved without changing the materials as much as possible based on the commercialized battery due to the aspects of cost, quality control, safety, etc.
Alloy negative electrode materials (such as silicon, germanium, tin and the like) have ultrahigh theoretical specific capacity, for example, the theoretical specific capacity of silicon is 4200mAh/g, the theoretical specific capacity of germanium is 1600mAh/g, and the theoretical specific capacity of tin is 994mAh/g, which are far higher than that of a traditional graphite negative electrode (372mAh/g), current research mainly focuses on using a high-capacity alloy negative electrode to replace or partially replace the traditional graphite negative electrode to improve the energy density of a lithium ion battery, and the research on prolonging the cycle life of the lithium ion battery by using the high-capacity alloy negative electrode as a lithium storage agent is not reported so far.
Disclosure of Invention
The invention provides a long-cycle-life lithium ion battery and a method for prolonging the cycle life of the lithium ion battery, aiming at the problem that the long cycle life of the lithium ion battery cannot be effectively prolonged in the prior art. According to the invention, the high-capacity alloy negative electrode material is introduced into the negative electrode as the lithium storage agent, and the discharge cut-off voltage is gradually reduced in stages in the battery cycle process, so that the active lithium stored in the lithium storage agent is gradually released in stages, and the active lithium which is irreversibly consumed in the battery long cycle process is supplemented, thereby achieving the purpose of prolonging the cycle life of the lithium ion battery.
In order to achieve the above purpose of the invention, the following technical solutions are specifically adopted:
the invention provides a long-cycle-life lithium ion battery, which comprises a positive electrode, a negative electrode, a diaphragm, electrolyte, a battery shell, a lug and a battery management system, wherein the negative electrode is made of graphite, a lithium storage agent, a conductive agent, a binder and a current collector, and the lithium storage agent is a high-capacity alloy negative electrode material; the discharge cut-off voltage is controlled by a battery management system, and when the battery capacity is attenuated to a set value, the discharge cut-off voltage of the lithium ion battery is automatically reduced.
Further, the battery is controlled by a battery management system, and when the battery capacity is attenuated to 70-90% of the initial rated capacity, the discharge cut-off voltage of the lithium ion battery is automatically reduced, wherein the reduction amplitude is 0.01-0.2V; preferably, when the battery capacity is attenuated to 80-85% of the initial rated capacity, the battery management system automatically reduces the discharge cut-off voltage of the lithium ion battery by 0.05-0.1V. The initial rated capacity refers to the capacity corresponding to the discharge cut-off voltage of the lithium ion battery discharged from the full charge state to the set first stage after the normal formation step.
Further, the first-stage discharge cut-off voltage is a voltage corresponding to the discharge capacity of the lithium ion battery formed by the graphite cathode without the lithium storage agent and the corresponding anode material being 60-90% of the full discharge capacity.
Further, the positive electrode material of the lithium ion battery is any one or a combination of more than two of lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel manganate, nickel cobalt manganese ternary positive electrode material, nickel cobalt aluminum ternary positive electrode material and lithium-rich manganese-based positive electrode material; the negative active material of the negative electrode is a graphite material.
In a preferred embodiment of the present invention, the positive electrode material of the lithium ion battery is lithium iron phosphate, and the negative electrode active material of the negative electrode contains 80 to 99 wt% of graphite.
According to the invention, a high-capacity alloy negative electrode material is introduced into the negative electrode plate of the lithium ion battery to serve as a lithium storage agent, the lithium storage agent mainly plays a role in storing active lithium, and the adding amount of the lithium storage agent is 0.5-20 wt%, preferably 0.95-8.55 wt% of the total weight of the electrode material (including graphite, the lithium storage agent, a conductive agent and a binder).
The lithium storage agent is a high-capacity alloy substance, such as one or a combination of more than two of silicon-based substances (silicon, silicon monoxide, silicon-carbon composite, carbon-coated silicon monoxide, doped silicon oxide, silicon alloy), germanium-based substances (germanium, germanium alloy, carbon-coated germanium and germanium-carbon compound) and tin-based substances (tin, tin alloy, carbon-coated tin and tin-carbon compound). Preferably, a silicon-based substance is preferred as a lithium storage agent in view of capacity and technical maturity; more preferably carbon-coated silica.
Further preferably, the particle size of the carbon-coated silica particles is 1 to 20 μm, and the carbon content is 1 to 8 wt%; the thickness of the carbon coating layer is 5-30 nm.
According to the invention, the addition of the lithium storage agent can be carried out in various ways, such as: 1) the lithium storage agent and the graphite material are premixed or are mechanically mixed for introduction during slurry preparation; 2) the lithium storage agent can also be introduced by forming a composite negative electrode with graphite through high-temperature sintering or deposition.
The lithium stored in the lithium storage agent of the present invention can be obtained in various ways, such as: 1) obtained from the positive electrode upon charging; 2) or by pre-lithiation or lithium supplementation techniques, including pre-lithiation or lithium supplementation of the negative electrode (e.g., addition of metallic lithium powder, ultra-thin metallic lithium, alloy negative electrodes using pre-lithiation, electrochemical pre-lithiation, etc.); 3) adding lithium supplement reagent (Li) into the diaphragm or the positive electrode5FeO4、Li5Fe5O8、Li2NiO2、Li2C2O4、Li3N、Li2O, etc.).
The lithium ion battery positive electrode comprises a positive active material, a conductive agent, a binder, a positive additive and a current collector, wherein the active material, the additive, the binder and the conductive agent are dispersed, mixed, stirred, viscosity-adjusted, coated, dried, rolled, cut and the like to obtain the lithium ion battery positive electrode piece.
The negative electrode of the lithium ion battery comprises a negative electrode active material, a lithium storage agent, a conductive agent, a binder and a current collector, and the active material, the lithium storage agent, the binder and the conductive agent are dispersed, mixed, stirred, viscosity adjusted, coated, dried, rolled, cut and the like to obtain the negative electrode plate of the lithium ion battery.
The second purpose of the invention is to provide a method for prolonging the cycle life of the lithium ion battery, when the battery capacity decays to 70-90%, preferably 80-85%, of the initial rated capacity in the cycle process of the long cycle life lithium ion battery, the discharge cut-off voltage is reduced by the battery management system to recover the battery capacity, when the battery capacity decays to the set value of the initial rated capacity again, the discharge cut-off voltage is reduced by the battery management system, and the operation is repeated until the discharge cut-off voltage is reduced to 1.5-2.5V, or the active lithium in the lithium storage agent is completely released.
Further, the method for prolonging the cycle life of the lithium ion battery comprises the following steps:
(S1) controlling the initial discharge cut-off voltage to be the voltage corresponding to the discharge capacity of the lithium ion battery formed by the graphite cathode without the lithium storage agent and the corresponding anode material to be 60-90% of the complete discharge capacity;
(S2) in the process of cyclic charge and discharge, controlling the battery through a battery management system, and reducing the discharge cut-off voltage of the battery when the capacity of the battery is attenuated to 70-90% of the initial rated capacity so as to recover the capacity of the battery;
(S3) repeating the step (S2) until the discharge cut-off voltage is decreased to 1.5-2.5V, or the active lithium in the lithium storage agent is completely released. At this time, the discharge cut-off voltage is further lowered, and the contribution to the cycle life of the battery is small.
Further, in the step (S1), when the positive electrode material is lithium iron phosphate, the initial discharge cut-off voltage is 2.9 to 3.1V, preferably 2.95 to 3.0V.
Further, in the step (S2), the discharge cut-off voltage is decreased by a range of 0.01 to 0.2V, preferably 0.05 to 0.1V. The magnitude of the reduction in the discharge cut-off voltage is such that the discharge cut-off voltage is reduced 3 to 20 times, preferably 5 to 15 times, during the entire cycle of the lithium ion battery. The reduction range of the discharge cut-off voltage is too large, so that the lithium storage agent is deeply involved in the battery cycle too early, the cycle life of the battery is not prolonged greatly, and in addition, the reduction range of the discharge cut-off voltage is too large, so that the capacity exerted by the battery after the discharge cut-off voltage is reduced may exceed the initial rated capacity.
The invention controls the discharge cut-off voltage of the battery in stages, controls the active lithium in the lithium storage agent to be released in stages, supplements the lithium consumed in the battery circulation process in time and obviously prolongs the cycle life of the lithium ion battery; the preparation method of the lithium ion battery with long cycle life provided by the invention is matched with the existing preparation process of the lithium ion battery, can be realized by only introducing a lithium storage agent during preparation of a negative electrode and controlling the discharge cut-off voltage in stages during normal cycle, and is convenient, simple, effective and strong in operability for improving the cycle life of the lithium ion battery.
Drawings
FIG. 1 is a battery cycling procedure of example 1;
figure 2 is the example 8 battery cycle results.
Detailed Description
The embodiment of the invention takes the lithium iron phosphate positive electrode as an example, and the practical exertion capacity of the lithium iron phosphate positive electrode is 145 mAh/g; the natural coated graphite is used as a negative electrode material, and the actual exertion capacity is 350 mAh/g. The embodiments of the present invention are only for further illustration and explanation of the technology of the present invention, and the present invention is not limited to the following embodiments, and any changes within the scope of the claims are included in the scope of the present invention.
Carbon-coated silica was purchased from Yi jin, Inc. under the brand HC 1500.
Example 1
(1) Lithium iron phosphate anode plate manufacturing methodPreparing: premixing 94 wt% of lithium iron phosphate positive electrode material, 4 wt% of conductive carbon (Super P) and 2 wt% of PVDF binder, adding N-methylpyrrolidone (NMP) solvent, mechanically stirring to prepare slurry, adjusting the viscosity of the slurry, and coating the slurry on two sides of an aluminum foil with the thickness of 0.013mm, wherein the loading capacity of the two sides is 30.7mg/cm2Then rolling the pole piece with the compaction density of 2.4g/cm3And cutting to obtain the lithium iron phosphate positive pole piece.
(2) Preparing a composite pole piece containing a lithium storage agent: the lithium storage agent is carbon-coated silicon monoxide, the actual specific capacity of the lithium storage agent is 1480mAh/g, and the mass ratio of graphite to silicon monoxide is 91: 9, premixing, mixing a graphite/silica mixed negative electrode with the weight percentage of 95% with a conductive agent (Super P) with the weight percentage of 1.5%, adding sodium carboxymethylcellulose (CMC) glue with the weight percentage of 1.1%, stirring and mixing, then adding styrene butadiene rubber emulsion (SBR) with the weight percentage of 2.4%, uniformly mixing, and adjusting the viscosity to obtain slurry, wherein the mass ratio of the graphite/silica mixed negative electrode to the conductive agent to the sodium carboxymethylcellulose to the styrene butadiene rubber emulsion is 95: 1.5: 1.1: 2.4. then coating the prepared slurry on two sides of a copper foil with the thickness of 0.008mm, wherein the loading capacity of the two sides is 11mg/cm2Rolling the pole piece to a compaction density of 1.55g/cm3And slitting to obtain the graphite/silicon monoxide composite negative pole piece.
(3) Assembling the soft package battery: and (2) laminating the positive pole piece, the negative pole piece and the polypropylene diaphragm by a laminating machine, sealing the laminated positive pole piece, the negative pole piece and the polypropylene diaphragm in an aluminum plastic film bag, drying, adding electrolyte (1mol/L lithium hexafluorophosphate/ethylene carbonate/diethyl carbonate/fluoroethylene carbonate), and sealing to obtain the soft package battery.
(4) Formation of a battery: the battery is respectively stood for 12 hours at normal temperature and 45 ℃, then the battery is formed at the magnification of 0.01C, and the battery is exhausted and sealed for the second time after the formation is finished.
(5) Battery circulation: the cell was subjected to a cycle test using a novice cell tester (model CT-4008-5V12A) according to the setup program shown in fig. 1: cycling is carried out under the multiplying power of 0.5C, the charge cut-off voltage is 3.65V, the discharge cut-off voltage is 3.0V, and the initial capacity of the battery is 1.48 Ah; when the battery capacity is attenuated to 80% of the initial capacity, namely 1.184Ah, the charge cut-off voltage is unchanged, the discharge cut-off voltage is reduced to 2.9V, charge and discharge cycles are carried out, and the battery capacity is recovered to 1.347 Ah; continuing to perform charge-discharge circulation of the lithium ion battery, when the battery capacity is attenuated to 80% of the initial capacity again, keeping the charge cut-off voltage unchanged, reducing the discharge cut-off voltage to 2.8V, performing charge-discharge circulation, and recovering the battery capacity to 1.321 Ah; the above operation was repeated, keeping the charge cut-off voltage at 3.65V, and the discharge cut-off voltage at 2.7V, 2.6V, and 2.5V, respectively. When the discharge cut-off voltage is reduced to 2.5V, the lithium ion battery keeps the charge cut-off voltage at 3.65V and the discharge cut-off voltage at 2.5V for cycling until the end.
Fig. 1 is a battery cycling procedure of example 1.
Example 2
The same as example 1 except that the mass ratio of graphite to silica in step (2) was 95: 5, the two-sided loading capacity of the obtained pole piece is 12.2mg/cm2。
Example 3
The process was the same as in example 1 except that the mass ratio of graphite to silica in step (2) was 99: 1, the capacity of the two sides of the obtained pole piece is 13.7mg/cm2。
Example 4
The rest is the same as the example 1, except that the prelithiation silicon monoxide is adopted as a lithium storage agent in the step (2), the capacity is 1350mAh/g, the first coulombic efficiency is 91 percent, and the double-sided loading capacity of the obtained pole piece is 11.2mg/cm2。
Example 5
The rest is the same as example 1, except that step (3) of soft-package battery assembly adopts coating with Li5FeO4The thickness of the lithium supplement agent coating of the polypropylene diaphragm is 5 mu m.
Example 6
The rest of the process was the same as example 1, except that after the coated graphite/silica electrode sheet was obtained in the step (2), the stable lithium metal powder was uniformly sprayed onto the surface of the electrode sheet (0.2 mg/cm) by dispersing it in a toluene solvent2) Then dried and rolledAnd pressing and cutting the blank, and then assembling the blank by using a soft package battery.
Example 7
The rest is the same as the example 1, except that 1% of Li is added in the preparation of the lithium iron phosphate positive pole piece in the step (1)5FeO4And (4) lithium supplement.
Example 8
The procedure was as in example 1 except that the battery was cycled in step (5) using a cycling program of: the discharge cut-off voltage was decreased by 0.05V each time the battery capacity was decreased to 80% of the initial capacity, i.e., the discharge cut-off voltage was 3.0V, 2.95V, 2.90V, 2.85V, 2.80V, 2.75V, 2.70V, 2.65V, 2.60V, 2.55V, 2.50V in this order at the time of the cycle. Figure 2 is the example 8 battery cycle results. The discharge cut-off voltage of the battery is sequentially reduced to 3.0V, 2.95V, 2.90V, 2.85V, 2.80V, 2.75V, 2.70V, 2.65V, 2.60V, 2.55V and 2.50V in the circulation process.
Comparative example 1
The rest is the same as the example 1, except that the cycling program adopted when the battery is cycled in the step (5) is as follows: the battery is circulated under the multiplying power of 0.5C, the cut-off voltage of charging is 3.65V, and the cut-off voltage of discharging is 2.5V; the cycle ends when the battery capacity decays to 80% of the initial capacity.
Comparative example 2
The rest is the same as the example 1, except that no lithium storage agent is added in the step (2), and the double-sided loading capacity of the prepared pole piece is 14.1mg/cm2In addition, the cycling procedure used when the battery was cycled in the step (5) was the same as that of example 1, that is, the charge cut-off voltage was 3.65V, the initial discharge cut-off voltage was 3.0V, and the discharge cut-off voltage was sequentially lowered to 2.9V, 2.8V, 2.7V, 2.6V, and 2.5V by the battery testing apparatus each time the battery capacity was decreased to 80% of the initial capacity.
TABLE 1
Figure BDA0003656330410000081
Table 1 shows a comparison of cycle performance of batteries prepared in different examples and comparative examples, and it can be seen that the cycle life of the battery is significantly increased by performing the cycle in a manner of adding a lithium storage agent to the negative electrode provided by the present invention and controlling the discharge cut-off voltage in stages, by comparing example 1 with comparative example 1 and comparative example 2. Furthermore, by comparing example 1 with examples 4-7, it can be seen that by combining the present invention with lithium supplementation and prelithiation techniques, the capacity exerted by the battery can be increased while the cycle life of the lithium ion battery can be significantly extended. By comparing example 1 with example 8, it can be seen that the reduction in the discharge cut-off voltage is reduced to be advantageous in further extending the cycle life of the battery.

Claims (10)

1. The lithium ion battery with long cycle life is characterized by comprising a positive electrode, a negative electrode, a diaphragm, electrolyte, a battery shell, a lug and a battery management system, wherein the negative electrode is made of graphite, a lithium storage agent, a conductive agent, a binder and a current collector, and the lithium storage agent is a high-capacity alloy negative electrode material; the discharge cut-off voltage is controlled by a battery management system, and when the battery capacity is attenuated to a set value, the discharge cut-off voltage of the lithium ion battery is automatically reduced.
2. The long-cycle-life lithium ion battery of claim 1, wherein the battery is controlled by a battery management system, and when the battery capacity decays to 70-90% of the initial rated capacity, the discharge cut-off voltage of the lithium ion battery is automatically reduced by 0.01-0.2V; preferably, when the battery capacity decays to 80-85% of the initial rated capacity, the battery management system automatically reduces the discharge cut-off voltage of the lithium ion battery by 0.05-0.1V.
3. The long cycle life lithium ion battery of claim 1, wherein the initial stage discharge cut-off voltage is the voltage corresponding to a discharge capacity of 60-90% of the full discharge capacity of a lithium ion battery comprising a graphite negative electrode without a lithium storage agent and a corresponding positive electrode material.
4. The long-cycle-life lithium ion battery of claim 1, wherein the positive electrode material of the lithium ion battery is any one or a combination of more than two of lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, ternary positive electrode material of nickel cobalt manganese, ternary positive electrode material of nickel cobalt aluminum, and lithium-rich manganese-based positive electrode material; the negative active material of the negative electrode is a graphite material;
preferably, the anode material of the lithium ion battery is lithium iron phosphate, and the graphite accounts for 80-99 wt% of the cathode active material of the cathode.
5. The long-cycle-life lithium ion battery according to claim 1, wherein the lithium storage agent is added in an amount of 0.5 to 20 wt%, preferably 0.95 to 8.55 wt%, based on the total weight of the electrode material.
6. The long-cycle-life lithium ion battery according to claim 1, wherein the lithium storage agent is a high-capacity alloy species such as one or a combination of two or more of silicon-based species (silicon, silicon monoxide, silicon-carbon composite, carbon-coated silicon monoxide, doped silicon monoxide, silicon alloy), germanium-based species (germanium, germanium alloy, carbon-coated germanium, germanium-carbon compound) and tin-based species (tin, tin alloy, carbon-coated tin, tin-carbon compound).
7. The long cycle life lithium ion battery of claim 6, wherein said lithium storage agent is carbon coated silica; preferably, the carbon-coated silica particles have a particle size of 1 to 20 μm and a carbon content of 1 to 8 wt%; the thickness of the carbon coating layer is 5-30 nm.
8. A method for prolonging the cycle life of a lithium ion battery is characterized by comprising the following steps: use of a long-cycle-life lithium-ion battery according to any of claims 1 to 8, wherein the battery capacity is restored by lowering the discharge cut-off voltage by the battery management system when the battery capacity decays to 70 to 90%, preferably 80 to 85%, of the initial rated capacity during the cycle, and by lowering the discharge cut-off voltage again by the battery management system when the battery capacity decays again to the set value of the initial rated capacity, and repeating the above operations until the discharge cut-off voltage is lowered to 1.5 to 2.5V, or the active lithium in the lithium storage agent is completely released.
9. The method of extending the cycle life of a lithium ion battery of claim 8, comprising the steps of:
(S1) controlling the initial discharge cut-off voltage to be the voltage corresponding to the discharge capacity of the lithium ion battery formed by the graphite cathode without the lithium storage agent and the corresponding anode material to be 60-90% of the complete discharge capacity;
(S2) in the process of cyclic charge and discharge, the battery is controlled by a battery management system, and when the battery capacity is attenuated to 70-90% of the initial rated capacity, the discharge cut-off voltage of the battery is reduced, so that the battery capacity is recovered;
(S3) repeating the step (S2) until the discharge cut-off voltage is reduced to 1.5-2.5V, or the active lithium in the lithium storage agent is completely released;
preferably, in the step (S2), the magnitude of the discharge cut-off voltage decrease is 0.01-0.2V, preferably 0.05-0.1V; the magnitude of the decrease in the discharge cut-off voltage is such that the discharge cut-off voltage decreases 3 to 20 times, preferably 5 to 15 times, during the entire cycle of the lithium ion battery.
10. The method for extending cycle life of lithium ion battery according to claim 9, wherein in step (S1), when the cathode material is lithium iron phosphate, its initial discharge cut-off voltage is 2.9-3.1V, preferably 2.95-3.0V.
CN202210560328.3A 2022-05-23 2022-05-23 Long-cycle-life lithium ion battery and method for prolonging cycle life of lithium ion battery Pending CN114784401A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024040996A1 (en) * 2022-08-23 2024-02-29 荣耀终端有限公司 Charging and discharging management method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024040996A1 (en) * 2022-08-23 2024-02-29 荣耀终端有限公司 Charging and discharging management method

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