A high-voltage electrolyte and a lithium-ion battery containing the same.

Abstract

The application provides a high-voltage electrolyte and a lithium ion battery containing the same. The electrolyte comprises an organic solvent, a lithium salt and an additive, wherein the additive comprises fluorine-containing lithium borate salt A as shown in formula 1 and / or fluorine-containing lithium borate salt B as shown in formula 2. In the application, the novel high-voltage positive electrode film-forming additive fluorine-containing lithium borate salt A and fluorine-containing lithium borate salt B are added in the electrolyte to improve the cycle performance of the battery at high voltage, and to improve the swelling problem of the battery at high voltage, thereby improving the safety performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and more particularly to a high-voltage electrolyte and a lithium-ion battery containing the same. Background Technology

[0002] With the rapid development of new energy, new materials, and new energy vehicles in recent years, lithium-ion batteries have seen increasingly widespread applications in high-tech fields, greatly promoting the development of the lithium-ion battery materials industry. High energy density and long lifespan lithium-ion batteries are ideal for electric vehicles and grid energy storage. Many researchers have focused on developing positive and negative electrode materials with higher specific capacity or positive electrode materials with higher average voltage, while less attention has been paid to advancements in electrolytes. In batteries cycling at 4.5 V or higher, the advantages of electrolyte additives in traditional carbonate electrolytes are diminished. This is because electrolyte solvents (such as carbonates) and / or salts (such as LiPF6) are unstable at high voltages and easily decompose, leading to irreversible damage to battery performance.

[0003] Conventional carbonate and lithium hexafluorophosphate systems decompose in batteries with voltages above 4.5V, resulting in poor cycle performance, poor high-temperature performance, and other performance degradation, which no longer fully meet the requirements of high-voltage lithium-ion batteries. Currently, no single additive can achieve all performance goals; instead, a combination of multiple additives is used to meet the battery performance requirements.

[0004] CN 108110321 A discloses a high-voltage electrolyte for lithium batteries, which uses sulfone additives to stabilize the high-voltage lithium-ion battery system and thus improve its electrochemical performance. Sulfone electrolytes are inexpensive and have an electrochemical window exceeding 5V, making them potential high-voltage electrolytes for lithium-ion batteries. However, sulfone solvents have problems such as high melting points, most sulfones being solid at room temperature, and poor compatibility with cathode materials.

[0005] CN 107528088A discloses a high-energy-density cathode material adapted to a high-voltage electrolyte. The cathode film-forming additive consists of tris(hexafluoroisopropyl)phosphate and nitrile additives, providing a high-voltage electrolyte suitable for charging voltages of 4.5~5.0V. Nitriles exhibit high thermal stability, good anodic stability, and a wide liquid temperature range. The most prominent feature is a wide electrochemical window; the oxidation resistance of single nitriles can reach 7V, making decomposition difficult in typical 5V high-voltage lithium-ion batteries. However, it has poor compatibility with anodes such as graphite or metallic lithium, and will polymerize at the anode, with the resulting polymers hindering lithium-ion insertion / extraction.

[0006] Therefore, how to prepare an electrolyte that is compatible with both negative and positive electrode materials, can be mass-produced at low cost, can improve the high-voltage performance of batteries, and can provide kinetic stability for the positive electrode is an important research direction in this field. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a high-voltage electrolyte and a lithium-ion battery containing the electrolyte.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] One objective of this invention is to provide a high-voltage electrolyte comprising an organic solvent, a lithium salt, and additives, wherein the additives include a fluorinated lithium borate salt A as shown in Formula 1 and / or a fluorinated lithium borate salt B as shown in Formula 2.

[0010] Formula 1 Equation 2, where R=C n H 2n+1 , 1≤n≤5, where the value of n can be 1, 2, 3, 4 or 5, etc., but is not limited to the listed values. Other unlisted values ​​within this range also apply.

[0011] This invention incorporates novel high-voltage positive electrode film-forming additives, fluorinated lithium borate salt A and fluorinated lithium borate salt B, into the electrolyte to improve the battery's cycle performance under high voltage and mitigate its expansion problem, thereby enhancing battery safety. Fluorinated lithium borate salt A and fluorinated lithium borate salt B are primarily used to form a film on the positive electrode surface. Compared to the electrolyte solvent, these additives have a lower oxidation potential and can preferentially decompose under high voltage to form a positive electrode protective film, reducing the contact between the electrolyte and the electrode, inhibiting the oxidative decomposition of the electrolyte, and thus improving the electrochemical performance of the lithium-ion battery.

[0012] As a preferred technical solution of the present invention, based on the mass of the electrolyte as 100%, the mass fraction of the fluorinated lithium borate salt A in the electrolyte is 1.5~2.5%, wherein the mass fraction can be 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4% or 2.5%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0013] Preferably, based on the mass of the electrolyte (100%), the fluorinated lithium borate salt B accounts for 0.5% to 1.5% of the electrolyte by mass. The mass fraction can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] As a preferred embodiment of the present invention, the additive further includes vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate.

[0015] Preferably, based on the mass fraction of the electrolyte being 100%, the vinylene carbonate accounts for 0.5% to 1.5% of the mass fraction of the electrolyte. The mass fraction can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, based on the mass fraction of the electrolyte being 100%, the mass fraction of the fluoroethylene carbonate in the electrolyte is 0.5% to 1.5%, wherein the mass fraction can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0017] Preferably, with the electrolyte having a mass fraction of 100%, the lithium difluorophosphate accounts for 0.2% to 0.8% of the electrolyte by mass. The mass fraction can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, or 0.8%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] As a preferred technical solution of the present invention, with the mass fraction of the electrolyte being 1000%, the additive accounts for 3.2-8% of the mass fraction of the electrolyte. The mass fraction can be 3.2%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or 8%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] As a preferred embodiment of the present invention, the organic solvent includes any one or a combination of at least two of ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, or propylene carbonate. Typical but non-limiting examples of such combinations include combinations of ethylene carbonate and methyl ethyl carbonate, combinations of methyl ethyl carbonate and diethyl carbonate, combinations of diethyl carbonate and dimethyl carbonate, or combinations of dimethyl carbonate and propylene carbonate.

[0020] Preferably, the organic solvent includes ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate.

[0021] Preferably, the mass ratio of ethylene carbonate, methyl ethyl carbonate and diethyl carbonate is (2~4):(5~7):1, wherein the mass ratio can be 2:7:1, 3:6:1 or 4:5:1, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] As a preferred embodiment of the present invention, with the electrolyte mass fraction as 100%, the organic solvent accounts for 77-86% of the electrolyte mass fraction. The mass fraction can be 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or 86%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0023] As a preferred embodiment of the present invention, the lithium salt includes lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide.

[0024] Preferably, the lithium salt comprises lithium hexafluorophosphate.

[0025] Preferably, the concentration of the lithium salt in the electrolyte is 0.8~1.2 mol / L, wherein the concentration may be 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L or 1.2 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] As a preferred technical solution of the present invention, with the mass fraction of the electrolyte being 100%, the lithium salt accounts for 10-15% of the mass fraction of the electrolyte. The mass fraction can be 10%, 11%, 12%, 13%, 14%, or 15%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] A second objective of the present invention is to provide a lithium-ion battery comprising the high-voltage electrolyte as described in one objective.

[0028] The lithium-ion battery also includes a positive electrode, a negative electrode, and a separator.

[0029] As a preferred embodiment of the present invention, the active material of the positive electrode includes lithium nickel cobalt manganese oxide.

[0030] Preferably, the active material of the negative electrode includes graphite.

[0031] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] The high-voltage electrolyte prepared in this invention is applied in lithium-ion batteries. When the potential is higher than 4.7V vs. Li + When / Li, LiNi can be stabilized. 0.6 Mn 0.2 Co 0.2 The surface of the (NMC622) positive electrode forms a CEI film at the positive electrode interface, thereby improving the battery's energy density, power, cycle performance, and other characteristics. Specifically, the battery can achieve a capacity retention rate of over 91.8%, a capacity recovery rate of over 94.2%, and a volume expansion of less than 2.5% when stored at 60℃ for 30 days. At 25℃, the capacity retention rate can reach over 92.4%, and at 45℃, the capacity retention rate can reach over 89.7%. Detailed Implementation

[0034] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0035] Example 1

[0036] This embodiment provides a high-voltage electrolyte:

[0037] High-voltage electrolytes include organic solvents, lithium salts, and additives;

[0038] The organic solvents include ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 3:6:1;

[0039] Lithium salts include lithium hexafluorophosphate at a concentration of 1 mol / L in the electrolyte;

[0040] The additives include: lithium borate A containing fluorine as shown in Formula 1, accounting for 2% of the electrolyte mass fraction (based on 100% of the electrolyte mass fraction). Formula 1, R=CH2), lithium difluorophosphate accounting for 0.5% of the electrolyte mass fraction, vinylene carbonate accounting for 1% of the electrolyte mass fraction, and fluoroethylene carbonate accounting for 1% of the electrolyte mass fraction.

[0041] Of which, based on the mass fraction of the electrolyte being 100%, the mass fraction of the organic solvent is 83%, the mass fraction of the lithium salt is 12.5%, and the mass fraction of the additive is 4.5%.

[0042] Example 2

[0043] This embodiment provides a high-voltage electrolyte:

[0044] High-voltage electrolytes include organic solvents, lithium salts, and additives;

[0045] The organic solvents include ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate in a mass ratio of 2:7:1;

[0046] Lithium salts include lithium hexafluorophosphate at a concentration of 0.8 mol / L in the electrolyte;

[0047] The additives include: 1.5% (by mass fraction of the electrolyte) of a fluorinated lithium borate salt A as shown in Formula 1 (…). Formula 1, R=C2H5), lithium difluorophosphate accounting for 0.2% of the electrolyte mass fraction, vinylene carbonate accounting for 0.5% of the electrolyte mass fraction, and fluoroethylene carbonate accounting for 0.5% of the electrolyte mass fraction.

[0048] Of which, based on the mass fraction of the electrolyte being 100%, the mass fraction of the organic solvent is 87.3%, the mass fraction of the lithium salt is 10%, and the mass fraction of the additive is 2.7%.

[0049] Example 3

[0050] This embodiment provides a high-voltage electrolyte:

[0051] High-voltage electrolytes include organic solvents, lithium salts, and additives;

[0052] The organic solvents include ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate in a mass ratio of 4:5:1;

[0053] Lithium salts include lithium hexafluorophosphate at a concentration of 1.2 mol / L in the electrolyte;

[0054] The additives include: a fluorinated lithium borate salt A as shown in Formula 1, comprising 2.5% of the electrolyte by mass fraction (based on 100% of the electrolyte mass fraction). Formula 1, R=C3H7), lithium difluorophosphate accounting for 0.8% of the electrolyte mass fraction, vinylene carbonate accounting for 1.5% of the electrolyte mass fraction, and fluoroethylene carbonate accounting for 1.5% of the electrolyte mass fraction.

[0055] Of which, based on the mass fraction of the electrolyte being 100%, the mass fraction of the organic solvent is 78.7%, the mass fraction of the lithium salt is 15%, and the mass fraction of the additive is 6.3%.

[0056] Example 4

[0057] This embodiment provides a high-voltage electrolyte:

[0058] High-voltage electrolytes include organic solvents, lithium salts, and additives;

[0059] The organic solvents include ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 3:6:1;

[0060] Lithium salts include lithium hexafluorophosphate at a concentration of 1 mol / L in the electrolyte;

[0061] The additives include: lithium borate salt B (as shown in Formula 2), comprising 1% of the electrolyte by mass fraction (based on 100% of the electrolyte mass fraction). Formula 2, R=C4H9), lithium difluorophosphate accounting for 0.5% of the electrolyte mass fraction, vinylene carbonate accounting for 1% of the electrolyte mass fraction, and fluoroethylene carbonate accounting for 1% of the electrolyte mass fraction.

[0062] Of which, based on the mass fraction of the electrolyte being 100%, the mass fraction of the organic solvent is 84%, the mass fraction of the lithium salt is 12.5%, and the mass fraction of the additive is 3.5%.

[0063] Example 5

[0064] This embodiment provides a high-voltage electrolyte:

[0065] High-voltage electrolytes include organic solvents, lithium salts, and additives;

[0066] The organic solvents include ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 3:6:1;

[0067] Lithium salts include lithium hexafluorophosphate at a concentration of 1 mol / L in the electrolyte;

[0068] The additives include: lithium borate salt B (as shown in Formula 2), comprising 1% of the electrolyte by mass fraction (based on 100% of the electrolyte mass fraction). Equation 2, R=C5H 11 ), comprising 2% by mass of the electrolyte, the fluorinated lithium borate salt A as shown in Formula 1 ( Formula 1, R=CH3), lithium difluorophosphate accounting for 0.5% of the electrolyte mass fraction, vinylene carbonate accounting for 1% of the electrolyte mass fraction, and fluoroethylene carbonate accounting for 1% of the electrolyte mass fraction.

[0069] Of which, based on the mass fraction of the electrolyte being 100%, the mass fraction of the organic solvent is 82%, the mass fraction of the lithium salt is 12.5%, and the mass fraction of the additive is 5.5%.

[0070] Example 6

[0071] In this embodiment, except that the fluorinated lithium borate salt A, which accounts for 2% of the electrolyte mass, is replaced with fluorinated lithium borate salt A, which accounts for 1% of the electrolyte mass, the mass fraction of the additive is replaced with 3.5%, and the electrolyte is replenished with an organic solvent, all other conditions are the same as in Example 1.

[0072] Example 7

[0073] In this embodiment, except that the fluorinated lithium borate salt A, which accounts for 2% of the electrolyte by mass, is replaced with fluorinated lithium borate salt A, which accounts for 3% of the electrolyte by mass, the mass fraction of the additive is replaced with 5.5%, and the electrolyte is replenished with an organic solvent, all other conditions are the same as in Example 1.

[0074] Example 8

[0075] In this embodiment, the only differences are that the 1% (by mass) fluorinated lithium borate B in the electrolyte is replaced with 2% (by mass) fluorinated lithium borate B in the electrolyte, and the mass fraction of the additive is changed to 4.5%. The electrolyte is replenished with an organic solvent, and all other conditions are the same as in Example 4.

[0076] Example 9

[0077] In this embodiment, the 1% (by mass) fluorinated lithium borate B in the electrolyte is replaced with 3% (by mass) fluorinated lithium borate B in the electrolyte. The mass fraction of the additive is changed to 5.5%. The electrolyte is replenished with an organic solvent. All other conditions are the same as in Example 4.

[0078] Example 10

[0079] In this embodiment, the only differences are that lithium difluorophosphate (0.5% by mass of electrolyte) is not added, the mass fraction of additive is replaced with 4%, and the electrolyte is replenished with organic solvent. All other conditions are the same as in Example 1.

[0080] Example 11

[0081] In this embodiment, except that vinylene carbonate (1% by mass of electrolyte) is not added, the mass fraction of additive is replaced with 3.5%, and the electrolyte is replenished with organic solvent, all other conditions are the same as in Example 1.

[0082] Example 12

[0083] In this embodiment, except that 1% fluoroethylene carbonate is not added to the electrolyte, the mass fraction of the additive is replaced with 3.5%, and the electrolyte is replenished with an organic solvent, all other conditions are the same as in Example 1.

[0084] Comparative Example 1

[0085] The only difference between this comparative example and Example 1 is that the fluorinated lithium borate salt A (2% by mass of electrolyte) was replaced with adiponitrile (2% by mass of electrolyte, a conventional high-voltage nitrile additive).

[0086] Comparative Example 2

[0087] The only difference between this comparative example and Example 1 is that the fluorinated lithium borate salt A (2% by mass of electrolyte) was replaced with sulfolane (2% by mass of electrolyte), while all other conditions were the same.

[0088] The electrolytes from Examples 1-12 and Comparative Examples 1-2 were assembled into lithium-ion batteries. A ternary lithium nickel cobalt manganese oxide material was used as the positive electrode material, graphite as the negative electrode material, a PP-PE composite separator as the separator, and an aluminum-plastic film as the outer shell to prepare a 5Ah lithium-ion battery. The lithium-ion batteries were subjected to high-temperature storage tests at 60℃, charge-discharge cycle tests at 25℃, and charge-discharge cycle tests at 45℃. The test results are shown in Table 1.

[0089] The method for the 60℃ high-temperature storage test is as follows: After capacity testing, the batteries of Examples 1-12 and Comparative Examples 1-2 are subjected to high-temperature storage experiments. First, the batteries are charged and discharged three times at 0.33C / 1C (4.7V / 3V) at room temperature (the capacity of the last discharge is recorded as DC0). Then, the fully charged (DOD=100SOC%) cells are placed in a 60℃ oven for storage for 30 days. After being taken out, they are left to stand at room temperature for 4 hours, and then discharged at 1C at room temperature (recorded as DC1). Then, three charge and discharge cycles are performed, and the capacity of the last discharge is recorded as DC2. The capacity retention rate and recovery rate of the lithium-ion battery are calculated.

[0090] Method for 25℃ charge-discharge cycle test:

[0091] At 25°C, the cells corresponding to Examples 1-12 and Comparative Examples 1-2 were charged to 4.7V under constant current and constant voltage at 1C, and then discharged to 3.0V under constant current at 1C. The capacity retention rate was calculated after 500 charge-discharge cycles.

[0092] 45℃ charge-discharge cycle test method:

[0093] At 45°C, the cells corresponding to Examples 1-12 and Comparative Examples 1-2 were charged to 4.7V under constant current and constant voltage at 1C, and then discharged to 3.0V under constant current at 1C. The capacity retention rate was calculated after 500 charge-discharge cycles.

[0094] Table 1

[0095]

[0096] The table above shows that, compared to the comparative examples, the cells in Examples 1-12 exhibited significantly improved performance in both ambient-temperature cycling and high-temperature storage. This indicates that adding high-voltage additives is superior to conventional additions of nitrile and sulfone additives in improving the battery's high-temperature storage and ambient-temperature cycling performance.

[0097] As can be seen from Examples 1-9, the performance is best when the amount of high voltage additive A is around 2%, and the performance is best when the amount of high voltage additive B is around 1%. It can significantly improve problems such as cell gas generation under high voltage. However, when A and B are added at the same time, the film resistance is large, so the capacity retention rate after cycling is not significantly better than that of adding them alone. Moreover, this type of high voltage additive is superior to ordinary nitrile and sulfone additives.

[0098] A comparison of Examples 1 and 10-12 shows that when lithium difluorophosphate, fluoroethylene carbonate, or vinylene carbonate are not added, the battery's high-temperature storage performance and capacity retention both decrease.

[0099] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are 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 within the protection scope of the present invention.

Claims

1. A high voltage electrolyte, characterized in that, The electrolyte comprises an organic solvent, a lithium salt and an additive, the additive comprises a fluorine-containing lithium borate salt A as shown in Formula 1; Formula 1, where R = CH2.

2. The electrolyte according to claim 1, characterized in that, The fluorine-containing lithium borate salt A accounts for 1.5-2.5% of the mass fraction of the electrolyte, based on 100% of the mass of the electrolyte.

3. The electrolyte of claim 1, wherein, The additive further comprises vinylene carbonate, fluoroethylene carbonate and lithium difluorophosphate.

4. The electrolyte according to claim 3, characterized in that, The vinylene carbonate accounts for 0.5-1.5% of the mass fraction of the electrolyte, based on 100% of the mass fraction of the electrolyte.

5. The electrolyte according to claim 3, characterized in that, The fluoroethylene carbonate accounts for 0.5-1.5% of the mass fraction of the electrolyte, based on 100% of the mass fraction of the electrolyte.

6. The electrolyte of claim 3, wherein, The lithium difluorophosphate accounts for 0.2-0.8% of the mass fraction of the electrolyte, based on 100% of the mass fraction of the electrolyte.

7. The electrolyte of claim 1, wherein The additive accounts for 3.2-8% of the mass fraction of the electrolyte, based on 100% of the mass fraction of the electrolyte.

8. The electrolyte of claim 1, wherein, The organic solvent comprises any one of vinyl carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate or propylene carbonate or a combination of at least two thereof.

9. The electrolyte of claim 1, wherein, The organic solvent comprises vinyl carbonate, methyl ethyl carbonate and diethyl carbonate.

10. The electrolyte of claim 9, wherein, The mass ratio of the vinyl carbonate, methyl ethyl carbonate and diethyl carbonate is (2-4):(5-7):

1.

11. The electrolyte of claim 1, wherein, The organic solvent accounts for 77-86% of the mass fraction of the electrolyte, based on 100% of the mass fraction of the electrolyte.

12. The electrolyte of claim 1, wherein, The lithium salt comprises lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide.

13. The electrolyte of claim 1, wherein, The lithium salt comprises lithium hexafluorophosphate.

14. The electrolyte of claim 1, wherein, The concentration of the lithium salt in the electrolyte is 0.8-1.2 mol / L.

15. The electrolyte of claim 1, wherein, The lithium salt accounts for 10-15% of the mass fraction of the electrolyte, based on 100% of the mass fraction of the electrolyte.

16. A lithium-ion battery, characterized by The lithium ion battery comprises the high-voltage electrolyte as claimed in any one of claims 1-15. The lithium ion battery further comprises a positive electrode, a negative electrode and a separator.

17. The lithium-ion battery of claim 16, wherein, The active material of the positive electrode comprises lithium nickel cobalt manganese oxide.

18. The lithium-ion battery of claim 16, wherein, The active material of the negative electrode comprises graphite.

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