Formation method of lithium ion battery and lithium ion battery

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a formation method of a lithium ion battery and the lithium ion battery. The formation method comprises the following steps: S1, obtaining an SOC-OCV curve by adopting a standard battery; s2, obtaining an SOC-DCR curve by adopting a standard battery; s31, if V1 < A < = V2, performing formation at a first charging rate; s32, forming at a second charging rate when V2 < B < = V section; the second charging rate is greater than the first charging rate; and S33, carrying out constant-voltage charging to a charging cut-off current, and carrying out third formation. The SOC range is determined according to the DCR range, then the OCV range is determined according to the SOC range, charging with smaller current is adopted in the V1-V2 range during formation, reaction of a silicon-containing negative electrode and lithium ions is promoted, more reversible active substances capable of being used for circulation are generated, so that the capacity is improved, charging with larger current is adopted in the V2-V range, and the formation efficiency is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion batteries, and particularly relates to a formation method of a lithium ion battery and the lithium ion battery. BACKGROUND

[0002] The capacity of a conventional graphite negative electrode lithium ion battery reaches a bottleneck, and in the production and processing of the lithium ion battery, a silicon and graphite doped negative electrode is used. Since silicon is a semiconductor, its conductivity is poorer than that of graphite, so there are certain differences between the processing of the silicon-containing negative electrode and the pure graphite negative electrode.

[0003] The formation process is a key link in the production process of the lithium battery and has an important influence on the performance of the lithium battery, especially the capacity. The conventional formation process uses a large formation current, which causes the resistance of lithium ions entering the interior of the silicon-containing negative electrode to become large, the lithium ions cannot fully react with the silicon-containing negative electrode, the active material is not activated, and cannot be used for subsequent cycles, so that the capacity of the lithium ion battery cannot be fully developed. However, using small current formation all the time will take a longer time, greatly reducing the production efficiency and making it impossible to produce on a large scale.

[0004] The existing step-by-step formation method has no theoretical guidance on when to select a large current and when to select a small current, and can only rely on repeated experiments for empirical summary, resulting in high research and development costs and a large waste of resources. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to overcome the defects that the existing lithium ion battery formation method has no systematic method guidance and cannot balance the formation efficiency and the capacity of the battery after formation, so as to provide a formation method of a lithium ion battery and the lithium ion battery.

[0006] To this end, the present application provides the following technical solutions: The present application protects a formation method of a lithium ion battery in the first aspect, wherein the formation method comprises the following steps: S1, constant current charging is performed on a standard battery to obtain a SOC-OCV standard curve, and the ordinate corresponding to the abscissa SOC of 0 is marked as V1; S2, constant current charging is performed on the standard battery at the same charging rate as S1, and DCR testing is performed to obtain a SOC-DCR standard curve, and the SOC interval corresponding to the DCR sudden drop interval is read from the graph, and the left end point of the SOC interval is brought into the SOC-OCV standard curve, and the ordinate corresponding to the left end point of the abscissa SOC interval is marked as V2; S3, formation is performed on a lithium ion battery to be formed, S31, when the voltage of the lithium ion battery is in the range of A, V1 S32, when the voltage of the lithium ion battery is in the B range, V2 截 S32, when the voltage of the lithium ion battery is in the B range, V2 The second charge rate is greater than the first charge rate. S33, when the voltage of the lithium ion battery reaches the charging cutoff voltage, the third formation is performed by charging to the charging cutoff current at a constant voltage.

[0007] In the present application, SOC (State of Charge) corresponds to the state of charge, which refers to the current storage capacity of the battery, usually expressed in percentage; since each SOC test point needs to go through a complete process, if the interval is too small (such as 1%), the test points will be very dense (100 points), which will take a long time and consume a lot of energy, which is not economical; if the interval is large, the curve change may not be observed, and the accuracy can be increased or decreased according to the actual situation, typically non-limiting, the interval is selected as 10%.

[0008] In the present application, OCV (Open Circuit Voltage) corresponds to the open circuit voltage, which refers to the voltage of the battery under no external load; since a small amount of electricity is applied, the OCV can reach a certain value, so in the SOC-OCV curve, when the horizontal coordinate is 0, the vertical coordinate can only approach 0 infinitely, but cannot be taken as 0, and actually has a certain initial value reading, typically non-limiting, the reading is 2.70-2.90V.

[0009] In the present application, DCR (Direct Current Resistance) corresponds to the direct current resistance, which refers to the resistance value of the battery under the action of direct current, and the unit is usually milliohm (mΩ); this test is used to evaluate the internal resistance characteristics of the battery, and indirectly reflects the health status of the battery.

[0010] In the present application, the V 截 The charging cutoff voltage is determined according to the actual situation, typically non-limiting, the positive active material is lithium nickel cobalt manganese ternary material (LiNi 0.9 Co 0.05 Mn 0.05 O2), and the negative active material includes silicon and graphite; when the mass ratio of silicon to graphite is 1:4, the cutoff voltage can be 4.2V; the charging cutoff current meets the provisions of GB / T 31484-2015 in the art, and the current obtained by multiplying the cutoff voltage by 0.02C is generally used as the charging cutoff current.

[0011] In the present application, the formation process of the lithium ion battery is carried out at 25℃ under standard atmospheric pressure.

[0012] In an alternative embodiment, in step S1, the charge rate of the constant current charging is 0.02-0.2C.

[0013] In an alternative embodiment, the first charging rate is 0.02-0.05C.

[0014] In an alternative embodiment, the second charging rate is 0.1-1C.

[0015] In an alternative embodiment, the standard battery and the lithium ion battery to be formed are the same in composition.

[0016] In an alternative embodiment, the standard battery is subjected to constant current charging at a charging rate of 0.02-0.2C throughout the process to complete formation.

[0017] In the present application, the principle of drawing the SOC-OCV standard curve is as follows: the standard battery is subjected to constant current charging to the charging cutoff voltage, and then is rested for 5-15 min, and the SOC and voltage are recorded, at this time the SOC is 100% SOC; the battery is subjected to constant current discharging to the discharging cutoff voltage, and then is rested for 5-15 min, and the SOC and voltage are recorded, at this time the SOC is 0% SOC; an SOC interval is set, the interval discharging capacity meeting one SOC interval is calculated, and after constant current charging to the cutoff voltage, the battery is discharged at the interval discharging capacity, and then is rested for 5-15 min after each discharging, and the voltage corresponding to X% SOC is obtained in turn, X includes 90, 80, 70, 60, 50, 40, 30, 20, and 10; and the SOC-OCV standard curve is drawn; in actual operation, the SOC-OCV standard curve can generally be directly read by an instrument, and typically and non-limitingly, the instrument model is BYT Test & Control NBT5V20AC32-T, and the SOC-OCV standard curve is directly read.

[0018] In an alternative embodiment, the drawing step of the SOC-DCR standard curve comprises: the standard battery is subjected to constant current charging at the same charging rate as S1, and is sequentially charged to X% SOC, X includes 10, 20, 30, 40, 50, 60, 70, 80, and 90, and resistance testing is performed.

[0019] In an alternative embodiment, the formula corresponding to the DCR sudden drop interval is (DCR n -DCR n+1 ) / DCR n >10%, wherein DCR n is the upper end point of the sudden drop interval, and DCR n+1 is the lower end point of the sudden drop interval.

[0020] In the present application, the resting time is selected and adjusted according to the actual battery system, and typically and non-limitingly, the resting time is 5-15 min.

[0021] In an alternative embodiment, the resistance test method is to record the battery voltage charged to the corresponding X% SOC as V X%静置 , and to recharge the battery charged to the corresponding X% SOC for 30-40 s, and to record the battery voltage after recharging as V X%充电结束 , and the DCR formula is (V X%充电结束 -V X%静置 ) / I.

[0022] In the present application, the recharging rate is determined according to the actual situation, and typically and non-limitingly, 1C is generally selected for charging, and the I (current) in the DCR formula is calculated according to the recharging rate selected and the battery capacity; the recharging time is only 30-40 s, and the DCR value can be obtained, which is approximately the DCR value corresponding to the X% SOC point value.

[0023] In an alternative embodiment, the negative active material in the lithium ion battery comprises silicon and component A.

[0024] In an alternative embodiment, the average particle size of the negative active material is 1-25 μm.

[0025] In an alternative embodiment, the mass ratio of the silicon to the component A is 1: (3-10).

[0026] In an alternative embodiment, the component A comprises graphite and / or hard carbon.

[0027] In an alternative embodiment, the positive active material in the lithium ion battery comprises any one of nickel-cobalt-manganese lithium ternary material and nickel-cobalt-aluminum ternary positive material, and typically and non-limitingly, the general formula of the nickel-cobalt-manganese lithium ternary material is LiNi 0.8-0.9 Co 0.03-0.05 Mn 0.03-0.05 O2.

[0028] In an alternative embodiment, the average particle size of the positive active material is 1-30 μm.

[0029] The present application protects a lithium ion battery treated by the foregoing formation method in a second aspect.

[0030] The technical solution of the present application has the following advantages: This invention provides a method for forming a lithium-ion battery, comprising the following steps: S1, performing constant current charging on a standard battery to obtain a SOC-OCV standard curve, and labeling the ordinate corresponding to the SOC being 0 as V1; S2, performing constant current charging on the standard battery using the same charging rate as in S1, and performing DCR testing to obtain a SOC-DCR standard curve, reading the SOC interval corresponding to the DCR drop interval from the curve, substituting the left endpoint of the SOC interval into the SOC-OCV standard curve, and labeling the ordinate corresponding to the left endpoint of the SOC interval as V2; S3, forming the lithium-ion battery to be formed, S31, when the voltage of the lithium-ion battery is in range A, V1 < A ≤ V2, performing constant current charging at a first charging rate for the first formation; S32, when the voltage of the lithium-ion battery is in range B, V2 < B ≤ V... 截 The second charging rate is constant current charging for the second formation; wherein the second charging rate is greater than the first charging rate; S33, when the voltage of the lithium-ion battery reaches the charging cutoff voltage, it is charged at constant voltage until the charging cutoff current, and the third formation is performed; the DCR of a lithium-ion battery is a common lithium battery parameter, which refers to the resistance characteristics exhibited inside the battery when a certain DC voltage is applied to the battery in a static or DC operating state, reflecting the battery's internal conductivity and energy transfer efficiency, etc.; due to the relatively high lithium intercalation potential of the silicon-containing anode, in the initial stage of charging, when the battery is at a low SOC At low voltages, graphite, due to its low lithium intercalation potential, is unlikely to undergo a large-scale lithium-ion intercalation reaction, while silicon can begin to accept lithium ions and react. Therefore, low SOC is the most active range for silicon anode reactions. Consequently, the DCR of batteries containing silicon anodes will significantly increase at low SOCs. This invention determines the SOC range for silicon reactions based on the DCR range, and then determines the OCV range based on the SOC range. During formation, a smaller charging current is used in the V1-V2 range to promote the reaction between the silicon anode and lithium ions, generating more reversible active materials that can be used for cycling, thereby increasing capacity. Meanwhile, in the V2-V... 截 The invention employs a larger current for charging within a certain range, which greatly improves the formation efficiency. Furthermore, the invention is universally applicable, not limited to any type of battery, and has a wide range of applications. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1is the SOC-OCV standard curve of Example 1; Figure 2 is the SOC-DCR standard curve of Example 1; Figure 3 is the SOC-OCV standard curve of Example 2; Figure 4 is the SOC-DCR standard curve of Example 2. DETAILED DESCRIPTION

[0033] The following examples are provided to better enable those skilled in the art to further understand and practice the application, and are not intended to limit the scope of the application in any way. Any product, example, or example that is similar or equivalent to the product, example, or example described in the disclosure, which is derived from the disclosure or from the combination of the disclosure and other prior art, falls within the scope of the disclosure.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application; the use of the terms "including," "comprising," or "having" and variations thereof herein is intended to be broad and encompass the terms "consisting of" and "consisting essentially of."

[0035] In the description of the present application, the technical terms "A", "B" and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the technical features indicated.

[0036] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive or alternative embodiments. It is explicitly and implicitly understood that the embodiments described herein can be combined.

[0037] The ranges disclosed herein are intended to be "open" ranges, i.e., the end values are not included in the given range. The ranges are intended to be defined by the selection of a lower limit and an upper limit, the lower limit and the upper limit defining the boundaries of the particular range. The ranges defined in this manner can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise indicated, a numerical range "a-b" indicates a shorthand manner of describing a range of values from "a" to "b", where "a" and "b" are actual numbers. For example, the numerical range "0-5" indicates that all actual numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand manner of describing those numerical values. Also, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter can be, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] In the description of the embodiments of the present application, the term "and / or" is merely an association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there can be three cases of A alone, A and B together, and B alone.

[0039] The specific experimental steps or conditions not indicated in the embodiments can be carried out according to the conventional experimental steps or conditions described in the literature in the art. The reagents or instruments not indicated by the manufacturer are conventional reagent products that can be obtained by purchase.

[0040] The SOC-OCV curves of the examples and comparative examples were obtained by using NBT5V20AC32-T of Bietest. The electrical tests of the examples and comparative examples were all carried out by using the blue cell test system.

[0041] Example 1 The present embodiment provides a formation method of a lithium ion battery, which comprises the following steps: The standard battery and the lithium ion battery to be formed have the same composition, both of which are cylindrical 18650 lithium ion batteries, and the nominal capacity is 3400 mAh. The positive active material is lithium nickel cobalt manganese oxide ternary material (LiNi 0.9 Co 0.05 Mn 0.05 O2), and the average particle size is 10 μm; the negative active material comprises silicon and graphite, and the mass ratio of silicon to graphite is 1:4, and the average particle size is 9 μm; The standard battery is charged at a constant current of 0.2C to 4.2V throughout the formation process; S1, the standard battery after formation is charged at a constant current of 0.1C to the charge cut-off voltage 4.2V, and is dormant for 10 min, and the SOC-OCV standard curve is as shown in Figure 1 Figure 1 ​Read V1 as 2.70V; S2, the standard battery after formation is charged at a rate of 0.1C, and is charged to X% SOC in turn, X includes 10, 20, 30, 40, 50, 60, 70, 80, 90, and after each charge is ended, it is dormant for 10 min, and the battery voltage charged to the corresponding X% SOC is recorded as V X%静置 , the battery charged to the corresponding X% SOC is recharged, the charging rate is 1C, and the charging time is 30s, and after each charge is ended, it is dormant for 5 min, and the battery voltage after recharging is recorded as V X%充电结束 , the DCR formula is (V X%充电结束 -V X%静置 ) / I 短程 , the X% SOC corresponding direct current resistance is obtained in turn, and the SOC-DCR standard curve is obtained, as shown in Figure 2 , (DCR 50% -DCR 60% ) / DCR 50% =13.7%>10%, so that 50% SOC is brought into the SOC-OCV standard curve in Figure 1 , and V2 is obtained as 3.88V; S3, the lithium ion battery to be formed is formed at 25°C under standard atmospheric pressure; S31, when in the range of V1-V2 (2.70-3.88V), constant current charging is carried out at a rate of 0.05C to carry out the first formation, and it is dormant for 10 min; S32, when in the range of V2-V 截 (3.88-4.2V), constant current charging is carried out at a rate of 0.2C to carry out the second formation; S33, when the voltage of the lithium ion battery reaches 4.2V, constant voltage charging is carried out to the cut-off current 68mA (3400mAh×0.02C) to carry out the third formation.

[0042] Example 2 The embodiment provides a formation method of a lithium ion battery, comprising the following steps: The standard battery and the lithium ion battery to be formed are the same in composition, and are both cylindrical 18650 batteries with a nominal capacity of 3200mAh; the positive active material is lithium nickel cobalt manganese ternary material (LiNi 0.9 Co 0.05 Mn 0.05 O2) with an average particle size of 10μm; the negative active material includes silicon and graphite, and the mass ratio of silicon to graphite is 1:9, and the average particle size is 9μm.

[0043] The standard battery is charged at a rate of 0.2C to 4.2V throughout the formation; S1, the standard battery after formation is charged at a rate of 0.1C to the cut-off voltage 4.2V, and sleeps for 10 minutes, and the SOC-OCV standard curve is obtained as shown in Figure 3 Figure 3 V1 is read as 2.90V; S2, the standard battery after formation is charged at a rate of 0.1C, and is sequentially charged to X% SOC, X including 10, 20, 30, 40, 50, 60, 70, 80, 90, and sleeps for 10 minutes after each charging, and the battery voltage charged to the corresponding X% SOC is recorded as V X%静置 , the battery charged to the corresponding X% SOC is recharged, the charging rate is 1C, and the charging time is 30s, and sleeps for 5 minutes after each charging, and the battery voltage after recharging is recorded as V X%充电结束 , the DCR formula is (V X%充电结束 -V X%静置 ) / I 短程 , and the SOC corresponding to the direct current resistance of X% is sequentially obtained, and the SOC-DCR standard curve is obtained as shown in Figure 4 30% -DCR 40% ) / DCR 30% =15.3%>10%, so that 30% SOC is brought into the SOC-OCV standard curve in Figure 3 , and the range V2 is 3.70V; S3, the lithium ion battery to be formed is formed at 25°C under standard atmospheric pressure; S31, when in the range of V1-V2 (2.90-3.70V), the first formation is carried out by constant current charging at a rate of 0.05C, and sleeps for 10 minutes; S32, when in the range of V2-V 截 (3.70-4.2V), the second formation is carried out by constant current charging at a rate of 0.2C; S33, when the voltage of the lithium ion battery reaches 4.2V, the third formation is carried out by constant voltage charging to the cut-off current 64mA (3200mAh×0.02C).

[0044] Comparative Example 1 The present comparative example provides a formation method of a lithium ion battery, comprising the following steps: The standard battery and the lithium ion battery to be formed are both cylindrical 18650 batteries, and the nominal capacity is 3200mAh; the positive active material is lithium nickel cobalt manganese ternary material (LiNi 0.9 Co 0.05 Mn 0.05 ​​O2), and the average particle size is 10 pm; the negative active material comprises silicon and graphite, and the mass ratio of silicon to graphite is 1:9, and the average particle size is 9 pm.

[0045] The standard battery is charged at 0.2C constant current to 4.2V throughout the formation process; The lithium ion battery to be formed is formed at 25°C under standard atmospheric pressure; (1) at V1-V 截 (2.90-4.2V), the first formation is performed by charging at 0.05C constant current to the cut-off voltage 4.2V; (2) when the voltage of the lithium ion battery reaches 4.2V, the second formation is performed by charging at constant voltage to the cut-off current 64mA (3200mAhx0.02C).

[0046] Comparative Example 2 The present comparative example provides a formation method of a lithium ion battery, comprising the following steps: The standard battery and the lithium ion battery to be formed are both cylindrical 18650 batteries, and the nominal capacity is 3200mAh; the positive active material is lithium nickel cobalt manganese oxide ternary material (LiNi 0.9 Co 0.05 Mn 0.05 O2), and the average particle size is 10 pm; the negative active material comprises silicon and graphite, and the mass ratio of silicon to graphite is 1:9, and the average particle size is 9 pm.

[0047] The standard battery is charged at 0.2C constant current to 4.2V throughout the formation process; The lithium ion battery to be formed is formed at 25°C under standard atmospheric pressure; (1) at V1-V 截 (2.90-4.2V), the first formation is performed by charging at 0.2C constant current to the cut-off voltage 4.2V; (2) when the voltage of the lithium ion battery reaches 4.2V, the second formation is performed by charging at constant voltage to the cut-off current 64mA (3200mAhx0.02C).

[0048] Test Example The formation time is recorded, and the time in Examples 1 and 2 is the total time of the first formation, the second formation and the third formation, and the time in Comparative Examples 1 and 2 is the first formation and the second formation time, and the results are shown in Table 1; Table 1

[0049] After the lithium ion battery is formed, the electrical performance test is performed by aging; The capacity test method is as follows: under room temperature, charging at 0.5C to 4.2V, after the voltage of the lithium battery reaches 4.2V, charging at constant voltage to the cut-off current of 0.02C, resting for 5 minutes, then discharging at 0.2C to 2.5V, recording the discharge capacity, and recording it as the 0.2C capacity; The specific test results are shown in Table 2. Table 2

[0050] The nominal capacity of Example 1 and other examples and comparative examples is different, which has no actual comparison meaning, so only the examples 2, comparative example 1 and comparative example 2 with the same nominal capacity are compared.

[0051] From the data in Table 1 and Table 2, it can be seen that the comparative example 1 with 0.05C rate small current throughout the formation, because the comparative example 1 uses 0.05C small rate for constant current charging throughout, the lithium ion can react more fully, and the capacity is even slightly higher than that of Example 2, but compared with Example 2, the formation time is greatly increased, the resource consumption is large, and the production efficiency is low, which does not have practical industrial value; and the comparative example 2 with 0.2C rate large current throughout the formation, although the formation time is short, but the capacity after formation is small, which cannot meet the actual application; the formation method of the present application can simultaneously consider the formation efficiency and the capacity of the battery after formation.

[0052] Obviously, the above examples are only examples for clearly illustrating, but not limit the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for forming a lithium-ion battery, characterized in that, The formation method includes the following steps: S1, constant current charging of standard battery to obtain SOC-OCV standard curve, and mark the ordinate corresponding to the horizontal axis SOC of 0 as V1; S2, the standard battery is charged with constant current using the same charging rate as S1, and DCR test is performed to obtain the SOC-DCR standard curve. The SOC interval corresponding to the DCR drop interval is read from the graph. The left endpoint of the SOC interval is substituted into the SOC-OCV standard curve, and the ordinate corresponding to the left endpoint of the SOC interval is marked as V2. S3, forming the lithium-ion battery to be formed. S31, when the voltage of the lithium-ion battery is in the range A, V1<A≤V2, it is charged at a constant current at the first charging rate to perform the first formation; S32, When the voltage of the lithium-ion battery is in the range B, V2 < B ≤ V 截 The second formation is carried out by constant current charging at the second charging rate. Wherein, the second charging rate is greater than the first charging rate; S33: When the voltage of the lithium-ion battery reaches the charging cutoff voltage, it is charged at a constant voltage until the charging cutoff current is reached, and then the third formation is performed.

2. The formation method according to claim 1, characterized in that, In step S1, the constant current charging rate is 0.02-0.2C; And / or, the first charging rate is 0.02-0.05C; And / or, the second charging rate is 0.1-1C.

3. The formation method according to claim 1 or 2, characterized in that, The standard battery and the lithium-ion battery to be formed have the same composition; And / or, the standard battery is charged at a constant current rate of 0.02-0.2C throughout the entire formation process.

4. The formation method according to any one of claims 1-3, characterized in that, The steps for plotting the SOC-DCR standard curve include: charging the standard battery with constant current using the same charging rate as S1, charging it sequentially to X% SOC, where X includes 10, 20, 30, 40, 50, 60, 70, 80, and 90%, and then performing resistance testing.

5. The formation method according to claim 4, characterized in that, The formula corresponding to the DCR drop interval is (DCR) n -DCR n+1 ) / DCR n >10%, of which DCR n DCR is the upper endpoint of the sudden drop interval. n+1 This is the lower endpoint of the sudden drop interval.

6. The formation method according to claim 4, characterized in that, The resistance testing method involves recording the voltage of a battery charged to the corresponding X% SOC as V. X%静置 Recharge the battery to the corresponding X% SOC for 30-40 seconds, and record the battery voltage after recharging as V. X%充电结束 The DCR formula is (V X%充电结束 -V X%静置 ) / I.

7. The formation method according to any one of claims 1-6, characterized in that, The negative electrode active material in the lithium-ion battery includes silicon and component A; Optionally, the average particle size of the negative electrode active material is 1-25 μm.

8. The formation method according to claim 7, characterized in that, The mass ratio of silicon to component A is 1:(3-10); Optionally, component A includes graphite and / or hard carbon.

9. The formation method according to any one of claims 1-8, characterized in that, The positive electrode active material in the lithium-ion battery includes any one of nickel-cobalt-manganese ternary materials and nickel-cobalt-aluminum ternary positive electrode materials. Optionally, the average particle size of the positive electrode active material is 1-30 μm.

10. A lithium-ion battery treated by the formation method according to any one of claims 1-9.

Images