Lithium ion battery

Abstract

The invention relates to a lithium ion battery in the technical field of lithium batteries, the lithium ion battery comprises a positive electrode, a negative electrode and an electrolyte, the positive electrode comprises spinel lithium manganese oxide, a first positive electrode lithium supplement agent and a second positive electrode lithium supplement agent; the consumption of the first positive electrode lithium supplement agent is greater than 70% when the first three cycles of the lithium ion battery are finished; the loss of the second positive electrode lithium supplement agent in 80-120 cycles of circulation of the lithium ion battery is completed. According to the invention, a double lithium supplement strategy is adopted, the active lithium loss in the first cycle or the first few cycles of the lithium ion battery containing spinel lithium manganese oxide is made up through the first positive electrode lithium supplement agent, and the active lithium loss in the first half of the whole battery life is made up through the second positive electrode lithium supplement agent; and the battery performance of the lithium ion battery containing the spinel lithium manganese oxide, especially the cycle performance at high temperature, is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a lithium ion battery. Background Art

[0002] Spinel lithium manganese oxide has attracted much attention and been widely used as a cathode material for lithium-ion batteries in recent years. Its unique spinel structure gives it high conductivity and fast ion diffusion ability, making it excellent in high-power applications. In addition, the raw materials of spinel lithium manganese oxide are abundant and low in cost, which has significant economic advantages compared to other cathode materials such as lithium cobalt oxide and lithium nickel cobalt manganese oxide.

[0003] However, spinel lithium manganese oxide also faces some challenges in practical applications.

[0004] For example, due to the unique high-temperature cycling performance of spinel lithium manganese oxide, it is prone to rapid decay in the early cycle process. This is mainly because manganese ions are easily dissolved into the electrolyte during the charge and discharge process, resulting in the destruction of the positive electrode material structure, thereby causing the active lithium to be lost rapidly in the early cycle of the battery; in the last 500 cycles, the decay rate of spinel lithium manganese oxide slows down, showing a trend of fast decay in the front and slow decay in the back.

[0005] Therefore, in view of the unique properties of spinel lithium manganese oxide, this application proposes a technical solution. According to the unique system of spinel lithium manganese oxide, a dual lithium replenisher strategy is adopted, using two positive electrode lithium replenishers to respectively compensate for the active lithium loss in the first cycle or the first few cycles of the lithium-ion battery containing spinel lithium manganese oxide and the active lithium loss in the first half of the entire battery life. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a lithium-ion battery, which adopts a dual lithium replenishment strategy to compensate for the loss of active lithium in the first cycle or the first few cycles of the lithium-ion battery containing spinel lithium manganese oxide and the loss of active lithium in the first half of the entire battery life. The technical solution of the present invention is specifically implemented as follows:

[0007] A lithium-ion battery comprises a positive electrode, a negative electrode and an electrolyte; the positive electrode comprises spinel lithium manganese oxide, a first positive electrode lithium replenisher and a second positive electrode lithium replenisher;

[0008] The first positive electrode lithium supplement is consumed in an amount greater than 70% at the end of the first three cycles of the lithium ion battery;

[0009] The second positive electrode lithium supplement is completely lost within 80-120 cycles of the lithium ion battery.

[0010] In the present invention, the first positive electrode lithium replenisher is used to compensate for the loss of active lithium in the first cycle and the first three cycles of a lithium-ion battery containing spinel lithium manganese oxide. It should be noted that the first positive electrode lithium replenisher in the present invention has the same function as the conventional first-charge lithium replenisher, which is to compensate for the loss of active lithium in the first charge cycle of the battery. The present invention does not specifically limit the first positive electrode lithium replenisher, as long as the first positive electrode lithium replenisher can meet the consumption of the lithium-ion battery at the end of the first three cycles of the lithium-ion battery. Greater than 70%. In practical applications, the first positive electrode lithium replenisher can be selected from one or a combination of lithium cobalt oxide, lithium nickel oxide, lithium ferrite, and Li2O2.

[0011] In addition, since the decay rate of the lithium-ion battery containing spinel lithium manganese oxide decreases in the later stage of the battery cycle, the demand for lithium supplement is not large. The present invention aims at the loss of active lithium in the early stage of the battery cycle, and supplements it through the second positive electrode lithium supplement, which can greatly improve the battery cycle performance of the lithium-ion battery containing spinel lithium manganese oxide. In the present invention, the performance of the second positive electrode lithium supplement is different from that of the first positive electrode lithium supplement. It must meet the slow release of lithium ions in the early stage of the battery cycle, and at the same time, it must meet the loss within 80-120 cycles of the lithium-ion battery.

[0012] Preferably, the consumption of the first positive electrode lithium replenisher in the first cycle of the lithium ion battery is 70%, and the consumption of the first positive electrode lithium replenisher in the first three cycles of the lithium ion battery is 80%;

[0013] The second positive electrode lithium supplement has an irreversible capacity loss of ≤20% in the first three cycles of the lithium ion battery, and an irreversible capacity loss of ≥80% in the first 100 cycles of the complete battery life of the lithium ion battery;

[0014] Preferably, the consumption of the first positive electrode lithium supplement in the first three cycles of normal use of the lithium ion battery is 90%;

[0015] The second positive electrode lithium supplement has an irreversible capacity loss of ≤10% in the first three cycles of the lithium ion battery, and an irreversible capacity loss of ≥90% in the first 100 cycles of the complete battery life of the lithium ion battery;

[0016] More preferably, the consumption of the first positive electrode lithium supplement in the first three cycles of normal use of the lithium ion battery is 95%;

[0017] The irreversible capacity loss of the second positive electrode lithium supplement in the first three cycles of the lithium ion battery is ≤5%.

[0018] Those skilled in the art should know that the greater the consumption of the lithium replenisher, the better the lithium replenishment effect. Therefore, it can be understood that the higher the consumption of the first positive electrode lithium replenisher in the first cycle and the first three cycles of normal use of the battery, the higher the short-term storage capacity recovery rate of the lithium-ion battery at high temperature. The greater the consumption of the second positive electrode lithium replenisher in the early cycles of the battery's full life, the higher the long-term storage capacity recovery rate of the lithium-ion battery at high temperature.

[0019] In addition, it should be noted that the "short term" referred to in the present invention refers to the first cycle and the first few cycles of the lithium-ion battery in normal use, while the "long term" referred to in the present invention is relative to the "short term", which still belongs to the early cycles of the battery's complete life.

[0020] Preferably, the charging cut-off voltage of the second positive electrode lithium supplement is greater than 4.2V.

[0021] It should be noted that the charging cut-off voltage of the second positive electrode lithium supplement is not a voltage control operation during battery charging, but a material property. During the charge and discharge cycle of a lithium-ion battery containing spinel lithium manganese oxide, since the charging cut-off voltage of spinel lithium manganese oxide is 4.2V, and the charging cut-off voltage of the second positive electrode lithium supplement is greater than 4.2V, it can be ensured that the addition of the second positive electrode lithium supplement will not affect the normal charging and discharging process of the lithium-ion battery.

[0022] Preferably, the first positive electrode lithium supplement has a lithium desorption potential lower than that of the spinel lithium manganese oxide.

[0023] Preferably, the lower voltage limit of the lithium-ion battery during the preparation process and the cycle process is greater than 3.0V, and the upper voltage limit is less than 4.2V.

[0024] Since the high voltage system has too high requirements for electrolytes, the existing technology cannot fully match the production process requirements and cost requirements of lithium-ion batteries containing spinel lithium manganese oxide. Therefore, based on the characteristics of lithium-ion batteries containing spinel lithium manganese oxide, the present invention adopts a low voltage system to prepare lithium-ion batteries, thereby avoiding the use of a high voltage system.

[0025] Preferably, the structural formula of the spinel manganese oxide is:

[0026] Li (1+b) Mn 2-b-c MO 4-a Q a ;

[0027] In the above formula, 0≤a≤1, 0≤b≤0.3, 0≤c≤1; M is at least one element selected from the group consisting of Mg, Al, Ni, Co, Fe, Cr, Cu, B, Ca, Nb, Mo, Sr, Sb, W, B, Ti, V, Zr and Zn, and Q is at least one element selected from the group consisting of N, F, S, and Cl.

[0028] In specific applications, a can be selected as any value between 0 and 1, b can be selected as any value between 0 and 0.3, and c can be selected as any value between 0 and 1. It is worth noting that when a is selected as 0, the spinel manganese oxide does not contain Q, and its molecular formula is Li (1+b) Mn 2-b-c MO4. For example, Li4Mn5O 12 . At this time, b=1 / 3, c=0.

[0029] Preferably, the charging cut-off voltage of the second positive electrode lithium supplement is less than 4.5V.

[0030] It should be noted that the charging cut-off voltage of the second positive electrode lithium supplement refers to the material properties, not the charging and discharging cut-off voltage of the battery in the actual process.

[0031] Preferably, the second positive electrode lithium supplement is a layered lithium manganese oxide, and its molecular structure is as follows:

[0032] The structural formula of layered lithium manganese oxide is as follows: xLi2MnO3-(1-a)LiMO2;

[0033] M is selected from any one of Al, Mg, Mn, Ni, Co, Cr, V, Fe, Cu, Zn, Ti and B, or two or more of the above elements used simultaneously.

[0034] Preferably, in the positive electrode, the content of the first positive electrode lithium replenisher is 3%-15%.

[0035] In specific applications, the content of the first positive electrode lithium supplement may be 3%, 5%, 8%, 10%, 15%, etc. The above values ​​are only examples and are not limiting.

[0036] Setting the content of the first positive electrode lithium replenisher within the above range can ensure the lithium replenishment effect of the first charging cycle and the first three cycles, while satisfying that the consumption of the first positive electrode lithium replenisher in the first cycle and the first three cycles is greater than 70%.

[0037] The present invention compensates for the loss of active lithium during the first cycle or the first three cycles of a lithium ion battery containing spinel lithium manganese oxide by using a first positive electrode lithium replenisher, and compensates for the loss of active lithium during the first half of the entire battery life in combination with a second positive electrode lithium replenisher, thereby solving the problem that the lithium ion battery containing spinel lithium manganese oxide is prone to rapid decay during the early cycle at high temperature. In addition, the second positive electrode lithium replenisher will be consumed in the early cycle of the battery, and is well adapted to the characteristics of the lithium ion battery containing spinel lithium manganese oxide in the last 500 cycles, in which the decay rate of the spinel lithium manganese oxide is reduced and the demand for lithium replenishment is not large, thereby preventing the lithium replenisher from accounting for too much and affecting the performance of the battery itself. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specific implementation methods are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the description and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusions.

[0040] In the description of the specific implementation methods of the present invention, the technical terms "first", "second", etc. 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 indicated technical features. In the description of the embodiments of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0041] Reference to "embodiments" in the present invention means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present invention may be combined with other embodiments.

[0042] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects before and after are in an "or" relationship.

[0043] Throughout the present invention, numerical values ​​represent approximate measures or limits of ranges to encompass minor deviations from given values ​​as well as embodiments having about the values ​​mentioned and embodiments having the exact values ​​mentioned. Except for the working examples provided at the end of the detailed description, all numerical values ​​of parameters, such as, amounts or conditions in this specification, including the appended claims, should be understood to be modified by the term "about" in all cases, regardless of whether "about" actually appears before the numerical value. "About" indicates that the stated numerical value allows some minor imprecision to be somewhat close to the exact value of the value; approximately or reasonably close to the value; almost. If the imprecision provided by "about" is not otherwise understood in this ordinary sense in the art, "about" as used in the present invention at least indicates the variation that can be produced by the ordinary methods of measuring and using such parameters. For example, "about" may include a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some aspects, optionally less than or equal to 0.1%.

[0044] Additionally, disclosure of ranges includes disclosure of all values ​​within the entire range and further divided ranges, including endpoints and sub-ranges given for such ranges.

[0045] Due to the unique high-temperature cycling performance of spinel lithium manganese oxide, it is prone to rapid decay in the early cycle process. This is mainly because manganese ions are easily dissolved into the electrolyte during the charge and discharge process, resulting in the destruction of the positive electrode material structure, thereby causing the active lithium to be lost rapidly in the early cycle of the battery; in the last 500 cycles, the decay rate of spinel lithium manganese oxide slows down, showing a trend of fast decay in the early stage and slow decay in the later stage.

[0046] In view of the characteristics of lithium-ion batteries containing spinel lithium manganese oxide, the present invention proposes a technical solution, which adopts a dual lithium replenishment strategy to compensate for the active lithium loss in the first cycle or the first few cycles of the lithium-ion battery containing spinel lithium manganese oxide and the active lithium loss in the first half of the entire battery life.

[0047] The embodiments of the present invention will be described in more detail below through examples and comparisons between the examples. It should be noted that the embodiments of the present invention are not limited to these examples.

[0048] Example 1

[0049] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged therebetween, the separator being made of conventional materials, and an electrolyte, the electrolyte being EC+1mol / LLiPF6. The preparation method of the lithium-ion battery is as follows:

[0050] 1. Preparation of negative electrode sheet:

[0051] 1. 94% of negative electrode active material graphite, 2% of CMC and conductive agent, 2% of SBR and 2% of Surpe-P were mixed and roll-formed to obtain a negative electrode active material layer.

[0052] 2. The negative electrode active material layer and the copper foil are rolled and laminated.

[0053] Second, the preparation of positive electrode:

[0054] 1. The positive electrode active material LMO (LiMnO4), the binder polyvinylidene fluoride (PVDF), and the conductive agent Surpe-P are mixed to prepare a positive electrode active material layer slurry, which is then coated on an aluminum foil and dried.

[0055] Third, a lithium-ion battery is prepared by conventional preparation methods using a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0056] Example 2

[0057] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged therebetween, the separator being made of conventional materials, and an electrolyte, the electrolyte being EC+1mol / LLiPF6. The preparation method of the lithium-ion battery is as follows:

[0058] 1. Preparation of negative electrode sheet:

[0059] 1. 94% of negative electrode active material graphite, 2% of CMC and conductive agent, 2% of SBR and 2% of Surpe-P were mixed and roll-formed to obtain a negative electrode active material layer.

[0060] 2. The negative electrode active material layer and the copper foil are rolled and laminated.

[0061] Second, the preparation of positive electrode:

[0062] 1. The positive electrode active material LMO (LiMnO4), the binder polyvinylidene fluoride (PVDF), and the conductive agent Surpe-P are mixed to prepare a positive electrode active material layer slurry, which is then coated on an aluminum foil and dried.

[0063] 2. The first positive electrode lithium supplement material Li2O2, the second positive electrode lithium supplement material layered lithium manganese oxide, the binder PVDF and the conductive agent Surpe-P are mixed, coated on the positive electrode active material layer and dried.

[0064] Layered lithium manganese oxide: 0.5Li2MnO3·0.5LiNi 0.4 Mn 0.6 O2

[0065] In the positive electrode sheet, LMO accounts for 94.7%, layered lithium manganese oxide accounts for 2.3%, and Li2O2 accounts for 3%.

[0066] Third, a lithium-ion battery is prepared by conventional preparation methods using a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0067] Example 3

[0068] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged therebetween, the separator being made of conventional materials, and an electrolyte, the electrolyte being EC+1mol / LLiPF6. The preparation method of the lithium-ion battery is as follows:

[0069] 1. Preparation of negative electrode sheet:

[0070] 1. 94% of negative electrode active material graphite, 2% of CMC and conductive agent, 2% of SBR and 2% of Surpe-P were mixed and roll-formed to obtain a negative electrode active material layer.

[0071] 2. The negative electrode active material layer and the copper foil are rolled and laminated.

[0072] Second, the preparation of positive electrode:

[0073] 1. The positive electrode active material LMO (LiMnO4), the binder polyvinylidene fluoride (PVDF), and the conductive agent Surpe-P are mixed to prepare a positive electrode active material layer slurry, which is then coated on an aluminum foil and dried.

[0074] 2. The first positive electrode lithium supplement material Li2O2, the second positive electrode lithium supplement material layered lithium manganese oxide, the binder PVDF and the conductive agent Surpe-P are mixed, coated on the positive electrode active material layer and dried.

[0075] Layered lithium manganese oxide: 0.5Li2MnO3·0.5LiNi 0.4 Mn 0.6 O2

[0076] In the positive electrode sheet, LMO accounts for 93.5%, layered lithium manganese oxide accounts for 3.5%, and Li2O2 accounts for 3%.

[0077] Third, a lithium-ion battery is prepared by conventional preparation methods using a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0078] Example 4

[0079] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged therebetween, the separator being made of conventional materials, and an electrolyte, the electrolyte being EC+1mol / LLiPF6. The preparation method of the lithium-ion battery is as follows:

[0080] 1. Preparation of negative electrode sheet:

[0081] 1. 94% of negative electrode active material graphite, 2% of CMC and conductive agent, 2% of SBR and 2% of Surpe-P were mixed and roll-formed to obtain a negative electrode active material layer.

[0082] 2. The negative electrode active material layer and the copper foil are rolled and laminated.

[0083] Second, the preparation of positive electrode:

[0084] 1. The positive electrode active material LMO (LiMnO4), the binder polyvinylidene fluoride (PVDF), and the conductive agent Surpe-P are mixed to prepare a positive electrode active material layer slurry, which is then coated on an aluminum foil and dried.

[0085] 2. The first positive electrode lithium supplement material Li2O2, the second positive electrode lithium supplement material layered lithium manganese oxide, the binder PVDF and the conductive agent Surpe-P are mixed, coated on the positive electrode active material layer and dried.

[0086] Layered lithium manganese oxide: 0.5Li2MnO3·0.5LiNi 0.4 Mn 0.6 O2

[0087] In the positive electrode sheet, LMO accounts for 92.2%, layered lithium manganese oxide accounts for 4.8%, and Li2O2 accounts for 3%.

[0088] Third, a lithium-ion battery is prepared by conventional preparation methods using a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0089] Example 5

[0090] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged therebetween, the separator being made of conventional materials, and an electrolyte, the electrolyte being EC+1mol / LLiPF6. The preparation method of the lithium-ion battery is as follows:

[0091] 1. Preparation of negative electrode sheet:

[0092] 1. 94% of negative electrode active material graphite, 2% of CMC and conductive agent, 2% of SBR and 2% of Surpe-P were mixed and roll-formed to obtain a negative electrode active material layer.

[0093] 2. The negative electrode active material layer and the copper foil are rolled and laminated.

[0094] Second, the preparation of positive electrode:

[0095] 1. The positive electrode active material LMO (LiMnO4), the binder polyvinylidene fluoride (PVDF), and the conductive agent Surpe-P are mixed to prepare a positive electrode active material layer slurry, which is then coated on an aluminum foil and dried.

[0096] 2. The first positive electrode lithium supplement material Li2O2, the second positive electrode lithium supplement material layered lithium manganese oxide, the binder PVDF and the conductive agent Surpe-P are mixed, coated on the positive electrode active material layer and dried.

[0097] Layered lithium manganese oxide: 0.5Li2MnO3·0.5LiNi 0.4 Mn 0.6 O2

[0098] In the positive electrode sheet, LMO accounts for 91.1%, layered lithium manganese oxide accounts for 5.9%, and Li2O2 accounts for 3%.

[0099] Third, a lithium-ion battery is prepared by conventional preparation methods using a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0100] Example 6

[0101] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged therebetween, the separator being made of conventional materials, and an electrolyte, the electrolyte being EC+1mol / LLiPF6. The preparation method of the lithium-ion battery is as follows:

[0102] 1. Preparation of negative electrode sheet:

[0103] 1. 94% of negative electrode active material graphite, 2% of CMC and conductive agent, 2% of SBR and 2% of Surpe-P were mixed and roll-formed to obtain a negative electrode active material layer.

[0104] 2. The negative electrode active material layer and the copper foil are rolled and laminated.

[0105] Second, the preparation of positive electrode:

[0106] 1. The positive electrode active material LMO (LiMnO4), the binder polyvinylidene fluoride (PVDF), and the conductive agent Surpe-P are mixed to prepare a positive electrode active material layer slurry, which is then coated on an aluminum foil and dried.

[0107] 2. The first positive electrode lithium supplement material Li2O2, the second positive electrode lithium supplement material layered lithium manganese oxide, the binder PVDF and the conductive agent Surpe-P are mixed, coated on the positive electrode active material layer and dried.

[0108] Layered lithium manganese oxide: 0.5Li2MnO3·0.5LiNi 0.4 Mn 0.6 O2

[0109] In the positive electrode sheet, LMO accounts for 89%, layered lithium manganese oxide accounts for 8%, and Li2O2 accounts for 3%.

[0110] Third, a lithium-ion battery is prepared by conventional preparation methods using a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0111] Example 7

[0112] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged therebetween, the separator being made of conventional materials, and an electrolyte, the electrolyte being EC+1mol / LLiPF6. The preparation method of the lithium-ion battery is as follows:

[0113] 1. Preparation of negative electrode sheet:

[0114] 1. 94% of negative electrode active material graphite, 2% of CMC and conductive agent, 2% of SBR and 2% of Surpe-P were mixed and roll-formed to obtain a negative electrode active material layer.

[0115] 2. The negative electrode active material layer and the copper foil are rolled and laminated.

[0116] Second, the preparation of positive electrode:

[0117] 1. The positive electrode active material LMO (LiMnO4), the binder polyvinylidene fluoride (PVDF), and the conductive agent Surpe-P are mixed to prepare a positive electrode active material layer slurry, which is then coated on an aluminum foil and dried.

[0118] 2. The first positive electrode lithium supplement material Li2O2, the second positive electrode lithium supplement material layered lithium manganese oxide, the binder PVDF and the conductive agent Surpe-P are mixed, coated on the positive electrode active material layer and dried.

[0119] Layered lithium manganese oxide: 0.5Li2MnO3·0.5LiNi 0.4 Mn 0.6 O2

[0120] In the positive electrode sheet, LMO accounts for 89.1%, layered lithium manganese oxide accounts for 5.9%, and Li2O2 accounts for 5%.

[0121] Third, a lithium-ion battery is prepared by conventional preparation methods using a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0122] Example 8

[0123] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged therebetween, the separator being made of conventional materials, and an electrolyte, the electrolyte being EC+1mol / LLiPF6. The preparation method of the lithium-ion battery is as follows:

[0124] 1. Preparation of negative electrode sheet:

[0125] 1. 94% of negative electrode active material graphite, 2% of CMC and conductive agent, 2% of SBR and 2% of Surpe-P were mixed and roll-formed to obtain a negative electrode active material layer.

[0126] 2. The negative electrode active material layer and the copper foil are rolled and laminated.

[0127] Second, the preparation of positive electrode:

[0128] 1. The positive electrode active material LMO (LiMnO4), the binder polyvinylidene fluoride (PVDF), and the conductive agent Surpe-P are mixed to prepare a positive electrode active material layer slurry, which is then coated on an aluminum foil and dried.

[0129] 2. The first positive electrode lithium supplement material Li2O2, the second positive electrode lithium supplement material layered lithium manganese oxide, the binder PVDF and the conductive agent Surpe-P are mixed, coated on the positive electrode active material layer and dried.

[0130] Layered lithium manganese oxide: 0.5Li2MnO3·0.5LiNi 0.4 Mn 0.6 O2

[0131] In the positive electrode sheet, LMO accounts for 96% and layered lithium manganese oxide accounts for 4%.

[0132] Third, a lithium-ion battery is prepared by conventional preparation methods using a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0133] Example 9

[0134] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged therebetween, the separator being made of conventional materials, and an electrolyte, the electrolyte being EC+1mol / LLiPF6. The preparation method of the lithium-ion battery is as follows:

[0135] 1. Preparation of negative electrode sheet:

[0136] 1. 94% of negative electrode active material graphite, 2% of CMC and conductive agent, 2% of SBR and 2% of Surpe-P were mixed and roll-formed to obtain a negative electrode active material layer.

[0137] 2. The negative electrode active material layer and the copper foil are rolled and laminated.

[0138] Second, the preparation of positive electrode:

[0139] 1. The positive electrode active material LMO (LiMnO4), the binder polyvinylidene fluoride (PVDF), and the conductive agent Surpe-P are mixed to prepare a positive electrode active material layer slurry, which is then coated on an aluminum foil and dried.

[0140] 2. The first positive electrode lithium supplement material Li2O2, the second positive electrode lithium supplement material layered lithium manganese oxide, the binder PVDF and the conductive agent Surpe-P are mixed, coated on the positive electrode active material layer and dried.

[0141] Layered lithium manganese oxide: 0.5Li2MnO3·0.5LiNi 0.4 Mn 0.6 O2

[0142] In the positive electrode sheet, LMO accounts for 96%, layered lithium manganese oxide accounts for 1%, and Li2O2 accounts for 3%.

[0143] Third, a lithium-ion battery is prepared by conventional preparation methods using a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0144] Example 10

[0145] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged therebetween, the separator being made of conventional materials, and an electrolyte, the electrolyte being EC+1mol / LLiPF6. The preparation method of the lithium-ion battery is as follows:

[0146] 1. Preparation of negative electrode sheet:

[0147] 1. 94% of negative electrode active material graphite, 2% of CMC and conductive agent, 2% of SBR and 2% of Surpe-P were mixed and roll-formed to obtain a negative electrode active material layer.

[0148] 2. The negative electrode active material layer and the copper foil are rolled and laminated.

[0149] Second, the preparation of positive electrode:

[0150] 1. The positive electrode active material LMO (LiMnO4), the binder polyvinylidene fluoride (PVDF), and the conductive agent Surpe-P are mixed to prepare a positive electrode active material layer slurry, which is then coated on an aluminum foil and dried.

[0151] 2. The first positive electrode lithium supplement material Li2O2, the binder PVDF and the conductive agent Surpe-P are mixed, coated on the positive electrode active material layer and dried.

[0152] In the positive electrode, LMO accounts for 85% and Li2O2 accounts for 15%.

[0153] Third, a lithium-ion battery is prepared by conventional preparation methods using a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0154] Comparative experiment:

[0155] Take 10 groups of samples from Examples 1-10, each group has 20 samples, and perform the following tests respectively:

[0156] 1. Test the endpoint lap number of the second positive electrode lithium supplement agent of each group of samples;

[0157] The test method is: set the cut-off voltage to the charging cut-off voltage of the second positive electrode lithium supplement. When the discharge capacity is not significantly different from the conventional 4.2V, it means that the active lithium based on the layered lithium manganese oxide has been consumed.

[0158] 2. Test the capacity recovery rate of each group of samples at 55°C for 7 days of high temperature storage;

[0159] ① Fully charge the battery at room temperature using the standard charging method; discharge the battery at 1C to the final discharge voltage, and calculate the remaining capacity, which is the initial capacity; fully charge the battery at room temperature using the standard charging method;

[0160] ②Store at 55±2℃ for 7 days;

[0161] ③ After standing at room temperature for 5 hours, discharge at 1C to the final discharge voltage, and calculate the remaining capacity, which is the recovery capacity;

[0162] Standard: 55℃ 7-day high temperature storage capacity recovery rate (%) = recovery capacity / initial capacity;

[0163] 3. Test the attenuation rate of each group of samples at 45°C and high temperature cycle for 100 weeks;

[0164] Temperature: 45℃±2℃

[0165] ① Charge at 1C or specified current to the end voltage, cut-off current 0.05C, and let stand for 30 minutes;

[0166] ②Discharge at 1C to the final discharge voltage, record the discharge capacity, and let stand for 30 minutes;

[0167] Cycle ①~②

[0168] Standard: 45℃ high temperature cycle 100 cycles attenuation rate (%) = discharge capacity of the 100th cycle / initial discharge capacity;

[0169] 45℃ high temperature cycle @80% SOC number of cycles = discharge capacity of the nth cycle / initial discharge capacity, record the value of n;

[0170] In the above tests, the average value of each test result of each group of samples is taken. The test results are shown in the following table.

[0171]

[0172] According to the above table:

[0173] 1. Consuming the first lithium supplement in the first three cycles is beneficial to the overall performance of the battery. If the first lithium supplement is not added and only the second lithium supplement is added, the second lithium supplement will be consumed too quickly during the early cycle, which is not conducive to maintaining the long cycle performance of the battery. However, adding an excessive amount of the first lithium supplement on the basis of satisfying the consumption of active lithium in the early stage will not improve the performance of the battery.

[0174] 3. The second positive electrode lithium replenisher is used to replenish lithium for the early decay phenomenon unique to spinel lithium manganese oxide during the early cycle. If the content of the second positive electrode lithium replenisher is too little, it cannot completely cover the active lithium loss of spinel lithium manganese oxide during the early cycle. If the number of cycles of consumption of the second positive electrode lithium replenisher exceeds 120, at this time, the decay phenomenon of spinel lithium manganese oxide has been alleviated, and the second positive electrode lithium replenisher cannot have a positive effect on the performance of the battery. Instead, it will cause the content of spinel lithium manganese oxide as the main active material to be too low, so that the disadvantage of the second lithium replenisher affects the performance of the battery.

[0175] It should be pointed out that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A lithium ion battery comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that: The positive electrode includes spinel lithium manganese oxide, a first positive electrode lithium replenisher and a second positive electrode lithium replenisher; The first positive electrode lithium supplement is consumed in an amount greater than 70% at the end of the first three cycles of the lithium ion battery; The second positive electrode lithium supplement is completely lost within 80-120 cycles of the lithium ion battery.

2. The lithium-ion battery according to claim 1, characterized in that The consumption of the first positive electrode lithium replenisher in the first cycle of the lithium ion battery is 70%, and the consumption of the first positive electrode lithium replenisher in the first three cycles of the lithium ion battery is 80%; The second positive electrode lithium supplement has an irreversible capacity loss of ≤20% in the first three cycles of the lithium ion battery, and an irreversible capacity loss of ≥80% in the first 100 cycles of the complete battery life of the lithium ion battery; Preferably, the consumption of the first positive electrode lithium supplement in the first three cycles of normal use of the lithium ion battery is 90%; The second positive electrode lithium supplement has an irreversible capacity loss of ≤10% in the first three cycles of the lithium ion battery, and an irreversible capacity loss of ≥90% in the first 100 cycles of the complete battery life of the lithium ion battery; More preferably, the consumption of the first positive electrode lithium supplement in the first three cycles of normal use of the lithium ion battery is 95%; The irreversible capacity loss of the second positive electrode lithium supplement in the first three cycles of the lithium ion battery is ≤5%.

3. The lithium ion battery according to claim 1, characterized in that The charging cut-off voltage of the second positive electrode lithium supplement is greater than 4.2V.

4. The lithium-ion battery according to claim 1, characterized in that: The first positive electrode lithium supplement has a lithium desorption potential lower than that of the spinel lithium manganese oxide.

5. A lithium ion battery according to claim 1, characterized in that: The lithium-ion battery has a lower voltage limit of more than 3.0V and an upper voltage limit of less than 4.2V during the preparation process and the cycle process.

6. A lithium ion battery according to claim 1, characterized in that: The structural formula of the spinel manganese oxide is: Li (1+b) Mn 2-b-c MO 4-a Q a ; In the above formula, 0≤a≤1, 0≤b≤0.3, 0≤c≤1; M is at least one element selected from the group consisting of Mg, Al, Ni, Co, Fe, Cr, Cu, B, Ca, Nb, Mo, Sr, Sb, W, B, Ti, V, Zr and Zn, and Q is at least one element selected from the group consisting of N, F, S, and Cl.

7. A lithium ion battery according to claim 1, characterized in that: The charging cut-off voltage of the second positive electrode lithium supplement is less than 4.5V.

8. A lithium ion battery according to claim 1, characterized in that: The second positive electrode lithium supplement is a layered lithium manganese oxide, and its molecular structure is as follows: The structural formula of layered lithium manganese oxide is as follows: xLi2MnO3-(1-a)LiMO2; M is selected from any one of Al, Mg, Mn, Ni, Co, Cr, V, Fe, Cu, Zn, Ti and B, or two or more of the above elements used simultaneously.

9. A lithium ion battery according to claim 10, characterized in that: In the positive electrode, the content of the first positive electrode lithium supplement agent is 3%-15%.

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