Negative electrode and battery

Abstract

The present invention relates to the field of batteries, and in particular to a negative electrode plate and a battery comprising the negative electrode plate. The negative electrode plate includes a current collector, a negative electrode active layer and a safety coating, wherein the negative electrode active layer is arranged on one side or both sides of the current collector, and the safety coating is arranged on the outer surface of the negative electrode active layer. The safety coating includes a lithium inorganic solid electrolyte, a binder and a flame retardant, and the lithium inorganic solid electrolyte is an oxide-type lithium inorganic solid electrolyte. Based on the total weight of the safety coating, the content of the oxide-type lithium inorganic solid electrolyte is 5-80% by weight. The negative electrode plate of the present invention can reduce the risk of short circuit caused by contact between the positive and negative electrodes when the battery cell is squeezed and punctured, while reducing the influence of the safety coating on lithium ion transmission, thereby minimizing or even eliminating the deterioration of the battery's electrical performance.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a negative electrode sheet and a battery comprising the negative electrode sheet. Background Art

[0002] As lithium-ion batteries evolve toward higher capacities and high-rate charge and discharge, higher safety requirements are being placed on them. Needle penetration and extrusion are key test items in lithium-ion battery safety testing. During testing, extrusion and steel needle penetration of the battery cell can partially fracture the positive and negative electrodes and separators, making it easy for the positive and negative electrodes to come into contact and cause a short circuit.

[0003] Currently, one method to improve safety performance is to apply ceramic safety coatings on the negative electrode surface and separator. However, ceramic materials are neither electron- nor ion-conductive, which can hinder the transfer of lithium ions in the battery cell and deteriorate the battery's electrical performance.

[0004] Therefore, it is very important to invent a battery that can improve safety performance without affecting electrical performance. Summary of the Invention

[0005] The present invention aims to overcome the aforementioned problems of the prior art and provides a negative electrode plate and a battery comprising the same. The negative electrode plate of the present invention is provided with a safety coating, which can prevent short circuits between the negative and positive electrodes during battery safety testing and prevent thermal runaway, providing dual protection. The safety coating can also transport lithium ions, effectively reducing the impact on electrical performance. The battery obtained from the negative electrode plate of the present invention has both good safety and electrical performance.

[0006] The inventors of the present invention have discovered that lithium inorganic solid electrolytes, as a material that does not conduct electrons but can conduct lithium ions, when used as a safety coating for negative electrode plates instead of ceramic materials, can not only protect the negative electrode during extrusion and puncture of the battery cell, reducing the risk of short circuits due to contact between the positive and negative electrodes; but also, compared with ceramic materials that have no ion transport function, lithium inorganic solid electrolytes can effectively reduce the impact of the safety coating on lithium ion transport, thereby minimizing or even eliminating the deterioration of the battery's electrical performance.

[0007] A first aspect of the present invention provides a negative electrode plate, which includes a current collector, a negative electrode active layer and a safety coating, wherein the negative electrode active layer is arranged on one side or both sides of the current collector, and the safety coating is arranged on the outer surface of the negative electrode active layer. The safety coating includes a lithium inorganic solid electrolyte, a binder and a flame retardant, and the lithium inorganic solid electrolyte is an oxide-type lithium inorganic solid electrolyte. Based on the total weight of the safety coating, the content of the oxide-type lithium inorganic solid electrolyte is 5-80 weight%.

[0008] A second aspect of the present invention provides a battery, comprising a negative electrode plate, which is the negative electrode plate described in the first aspect of the present invention.

[0009] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0010] (1) The negative electrode sheet of the present invention can reduce the risk of short circuit caused by contact between the positive and negative electrodes when the battery cell is squeezed and punctured, while reducing the impact of the safety coating on lithium ion transmission, thereby minimizing or even eliminating the deterioration of the battery's electrical performance;

[0011] (2) The negative electrode plate of the present invention can release CO2 and water when heated, thereby reducing the concentration of combustion gas and blocking the flame retardant effect of O2, thereby providing dual protection for the safety performance of the battery.

[0012] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Shown is a schematic diagram of the negative electrode structure of an example of the present invention.

[0014] Description of Reference Numerals

[0015] 1-current collector;

[0016] 2-negative electrode active layer;

[0017] 3-Safety coating. DETAILED DESCRIPTION

[0018] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0019] A first aspect of the present invention provides a negative electrode plate, which includes a current collector, a negative electrode active layer and a safety coating, wherein the negative electrode active layer is arranged on one side or both sides of the current collector, and the safety coating is arranged on the outer surface of the negative electrode active layer. The safety coating includes a lithium inorganic solid electrolyte, a binder and a flame retardant, and the lithium inorganic solid electrolyte is an oxide-type lithium inorganic solid electrolyte. Based on the total weight of the safety coating, the content of the oxide-type lithium inorganic solid electrolyte can be 5-80 weight%.

[0020] Preferably, based on the total weight of the safety coating, the content of the oxide-type lithium inorganic solid electrolyte is 20-60 wt%.

[0021] More preferably, based on the total weight of the safety coating, the content of the oxide-type lithium inorganic solid electrolyte is 35-45 wt%.

[0022] Figure 1 This is a schematic diagram of the negative electrode plate structure of an example of the present invention. The negative electrode plate includes a current collector 1, a negative electrode active layer 2 and a safety coating 3. The negative electrode active layer 2 is arranged on both sides of the current collector 1, and the safety coating 3 is arranged on the outer surface of the negative electrode active layer 2.

[0023] In another embodiment of the present invention, the negative electrode plate includes a current collector 1, a negative electrode active layer 2 and a safety coating 3, wherein the negative electrode active layer 2 is arranged on one side of the current collector 1, and the safety coating 3 is arranged on the outer surface of the negative electrode active layer 2.

[0024] In this document, the terms "lithium inorganic solid electrolyte" and "oxide-type lithium inorganic solid electrolyte" have the conventional meanings in the art. The term "lithium inorganic solid electrolyte," also known as a lithium fast ion conductor, generally refers to an inorganic solid substance with high ionic conductivity. "Lithium inorganic solid electrolyte" further includes "oxide-type lithium inorganic solid electrolyte," "sulfide-type lithium inorganic solid electrolyte," and "halide-type lithium inorganic solid electrolyte."

[0025] The inventors of the present invention have discovered that the specific selection of an oxide-type lithium inorganic solid electrolyte can better improve the cycle performance and rate performance of the battery.

[0026] Preferably, the oxide-type lithium inorganic solid electrolyte is selected from at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium aluminum silicon oxide, lithium aluminum titanium phosphorus oxide, lithium aluminum titanium phosphate and modified dopants thereof.

[0027] Preferably, the modified doping element of the modified dopant includes at least one of Ta, Nb, Mn, Al, Cr, Ga, Sc, Sm, In, Lu, Y, Si and La.

[0028] In one embodiment, the oxide-type lithium inorganic solid electrolyte is Ga-doped lithium lanthanum zirconium oxide, namely Li 6.7 Ga 0.1 La3Zr2O 12 .

[0029] In one embodiment, the oxide-type lithium inorganic solid electrolyte is Nb-doped lithium lanthanum zirconium oxide, namely Li 6.9 La3Zr 1.9 Nb 0.1 O12 .

[0030] In one embodiment, the oxide-type lithium inorganic solid electrolyte is Ga and Nb co-doped lithium lanthanum zirconium oxide, namely Li 6.1 Ga 0.1 La3Zr 1.4 Nb 0.6 O 12 .

[0031] In a specific embodiment, the oxide-type lithium inorganic solid electrolyte is lithium aluminum titanium phosphate.

[0032] In another specific embodiment, the oxide-type lithium inorganic solid electrolyte is lithium lanthanum zirconium oxide.

[0033] In another embodiment, the oxide-type lithium inorganic solid electrolyte is Sn-doped lithium lanthanum zirconium oxide, i.e. Li7La3Zr 1.3 Sn 0.3 O 12 .

[0034] The oxide-type lithium inorganic solid electrolyte can be obtained commercially. All commercially available oxide-type lithium inorganic solid electrolytes can be used in the negative electrode plate to achieve good results.

[0035] The binder is, for example, selected from at least one of acrylic acid-modified copolymer polyvinylidene fluoride (Ac-PVDF), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyvinyl alcohol (PVP), polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), acrylic acid and carboxymethyl cellulose.

[0036] Based on the total weight of the safety coating, the content of the binder may be 1-5 wt %.

[0037] In a specific embodiment, the binder is polyvinylidene fluoride (PVDF).

[0038] The flame retardant is selected from at least one of layered double metal hydroxides. Based on the total weight of the safety coating, the content of the flame retardant may be 5-80% by weight.

[0039] Preferably, based on the total weight of the safety coating, the content of the flame retardant may be 20-60 wt%.

[0040] More preferably, based on the total weight of the safety coating, the content of the flame retardant may be 35-45 wt%.

[0041] Preferably, the layered double hydroxide is at least one selected from the group consisting of Li-Al-hydrotalcite, Mg-Al-hydrotalcite, Mg-Fe-hydrotalcite, Ni-Al-hydrotalcite, Ni-Fe-hydrotalcite, Co-Al-hydrotalcite, Mn-Al-hydrotalcite and Zn-Al-hydrotalcite.

[0042] In a specific embodiment, the layered double hydroxide is Mg-Al-hydrotalcite.

[0043] In another specific embodiment, the layered double hydroxide is Ni-Fe-hydrotalcite.

[0044] As used herein, the term "layered double hydroxide" has the conventional meaning in the art. Layered double hydroxides, also known as hydrotalcite-like compounds, include hydrotalcite and hydrotalcite-like compounds. These are hydroxides composed of two or more metal elements and possessing a layered crystal structure similar to that of hydrotalcite. The chemical formula is: Among them, M I =Mg 2+ 、Ni 2+ 、Fe 2+ 、Co 2+ 、Mn 2+ etc., M. II =Al 3+ 、Fe 3+ 、Ti 4+ etc., A. n- is the interlayer anion, and m is the number of interlayer water molecules.

[0045] The layered double metal hydroxide can be obtained commercially. All commercially available layered double metal hydroxides can be used in the negative electrode sheet to achieve good results.

[0046] The safety coating further comprises a material capable of embedding lithium ions. Based on the total weight of the safety coating, the content of the material capable of embedding lithium ions is 10-30% by weight.

[0047] Preferably, based on the total weight of the safety coating, the content of the material capable of inserting lithium ions is 15-25% by weight.

[0048] The inventors of the present invention have discovered that when a safety coating contains a material capable of intercalating lithium ions, it can significantly improve the battery's cycle and rate performance. This may be because, in the present invention, the safety coating contains a relatively low content of the material capable of intercalating lithium ions, resulting in more contact sites with the surrounding electrolyte and solid electrolyte, providing more lithium ion migration channels and thus improving the battery's cycle and rate performance.

[0049] Preferably, the material capable of inserting lithium ions is selected from at least one of graphite, amorphous carbon, hard carbon and silicon.

[0050] In a specific embodiment, the material capable of inserting lithium ions is graphite.

[0051] In another specific embodiment, the material capable of inserting lithium ions is amorphous carbon.

[0052] In another specific embodiment, the material capable of inserting lithium ions is hard carbon.

[0053] The inventors of the present invention have discovered that when the oxide-type lithium inorganic solid electrolyte and the flame retardant are present in a specific ratio, the comprehensive performance of safety performance and electrochemical performance can be further improved.

[0054] The mass ratio of the oxide-type lithium inorganic solid electrolyte to the flame retardant is preferably 1:(0.8-1.3).

[0055] The inventors of the present invention have found that when the thickness of the safety coating is 5-20 μm, it is possible to ensure the safety performance of the battery without affecting the electrical performance of the battery and the volume energy density of the battery cell.

[0056] The thickness of the safety coating may be 1-40 μm, for example 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm and 40 μm.

[0057] Preferably, the safety coating has a thickness of 5-20 μm.

[0058] In the present invention, the thickness of the safety coating refers to the thickness of the safety coating on the outer surface of one side of the negative electrode plate.

[0059] The negative electrode plate of the present invention can reduce the risk of short circuit caused by contact between the positive and negative electrodes when the battery cell is squeezed and punctured, while reducing the impact of the safety coating on lithium ion transmission, thereby minimizing or even eliminating the deterioration of the battery's electrical performance; the flame retardant in the safety coating can prevent the temperature from rising sharply and reduce the oxygen concentration, thereby preventing thermal runaway, playing a dual role in protecting the battery, improving the pass rate of puncture, and solving the battery's safety problems.

[0060] A second aspect of the present invention provides a battery, characterized in that the battery includes a negative electrode plate, and the negative electrode plate is the negative electrode plate described in the first aspect of the present invention.

[0061] The components of the battery other than the negative electrode plate (such as the positive electrode plate, separator, electrolyte, etc.) and the assembly method can be carried out according to conventional methods in the field and will not be described in detail here.

[0062] The present invention will be described in detail below through examples. The examples described in the present invention are only some examples of the present invention, not all examples. All other examples obtained by persons of ordinary skill in the art based on the examples of the present invention without creative work are within the scope of protection of the present invention.

[0063] In the following examples, unless otherwise specified, all materials used were commercially available analytical grade.

[0064] The following group I of embodiments is used to illustrate the negative electrode sheet of the present invention.

[0065] Example I1

[0066] Graphite, conductive carbon, carboxymethyl cellulose and styrene-butadiene rubber (SBR) were mixed according to 97.0 parts by mass, 0.5 parts by mass, 1.3 parts by mass and 1.2 parts by mass, respectively, and stirred evenly at high speed using a ball mill. The mixture was coated on copper foil using a coater, and dried to remove ionized water to obtain a copper foil coated with a negative electrode active layer.

[0067] 35 wt% of lithium aluminum titanium phosphate, 5 wt% of polyvinylidene fluoride (PVDF), 45 wt% of Mg-Al-hydrotalcite and 15 wt% of graphite were mixed in N-methylpyrrolidone (NMP), stirred evenly at high speed using a ball mill, coated on the outer surface of the negative electrode active layer using a coater, dried, and the N-methylpyrrolidone (NMP) was removed to obtain a negative electrode sheet with a safety coating coated on the outside of the negative electrode active layer, wherein the thickness of the safety coating was 10 μm.

[0068] Example 12

[0069] Graphite, conductive carbon, carboxymethyl cellulose and styrene-butadiene rubber (SBR) were mixed according to 97.0 parts by mass, 0.5 parts by mass, 1.3 parts by mass and 1.2 parts by mass, respectively, and stirred evenly at high speed using a ball mill. The mixture was coated on copper foil using a coater, and dried to remove ionized water to obtain a copper foil coated with a negative electrode active layer.

[0070] 45 wt% of lithium aluminum titanium phosphate, 5 wt% of polyvinylidene fluoride (PVDF), 35 wt% of Mg-Al-hydrotalcite and 15 wt% of amorphous carbon were mixed in N-methylpyrrolidone (NMP), stirred evenly at high speed using a ball mill, coated on the outer surface of the negative electrode active layer using a coater, dried, and the N-methylpyrrolidone (NMP) was removed to obtain a negative electrode sheet coated with a safety coating on the outside of the negative electrode active layer, wherein the thickness of the safety coating was 10 μm.

[0071] Example 13

[0072] Graphite, conductive carbon, carboxymethyl cellulose and styrene-butadiene rubber (SBR) were mixed according to 97.0 parts by mass, 0.5 parts by mass, 1.3 parts by mass and 1.2 parts by mass, respectively, and stirred evenly at high speed using a ball mill. The mixture was coated on copper foil using a coater, and dried to remove ionized water to obtain a copper foil coated with a negative electrode active layer.

[0073] 40 wt% of lithium aluminum titanium phosphate, 5 wt% of polyvinylidene fluoride (PVDF), 40 wt% of Mg-Al-hydrotalcite and 15 wt% of hard carbon were mixed in N-methylpyrrolidone (NMP), stirred evenly at high speed using a ball mill, coated on the outer surface of the negative electrode active layer using a coater, dried, and the N-methylpyrrolidone (NMP) was removed to obtain a negative electrode sheet with a safety coating coated on the outside of the negative electrode active layer, wherein the thickness of the safety coating was 10 μm.

[0074] Example 14

[0075] This group of examples is used to illustrate the impact of changing the ratio of oxide-type lithium inorganic solid electrolyte to flame retardant in the safety coating of the negative electrode.

[0076] This group of examples was carried out with reference to Example I1, except that the ratio of lithium aluminum titanium phosphate and Mg-Al-hydrotalcite was changed, specifically:

[0077] Example 14a

[0078] Lithium aluminum titanium phosphate is 15% by weight, polyvinylidene fluoride (PVDF) is 5% by weight, Mg—Al hydrotalcite is 70% by weight, and graphite is 10% by weight.

[0079] Example 14b

[0080] Lithium aluminum titanium phosphate is 70% by weight, polyvinylidene fluoride (PVDF) is 5% by weight, Mg—Al hydrotalcite is 15% by weight, and graphite is 10% by weight.

[0081] Example 15

[0082] This group of examples is used to illustrate the impact of using other oxide-type lithium inorganic solid electrolytes in the safety coating of the negative electrode plate.

[0083] This group of examples was carried out with reference to Example I1, except that the oxide-type lithium inorganic solid electrolyte was changed, specifically:

[0084] Example I5a, replacing lithium aluminum titanium phosphate with lithium lanthanum zirconium oxide having the same mass fraction;

[0085] Example I5b, replacing lithium aluminum titanium phosphate with lithium lanthanum titanate having the same mass fraction;

[0086] Example 15c, lithium aluminum titanium phosphate is replaced by Sn-doped lithium lanthanum zirconium oxide with the same mass fraction, namely Li7La3Zr 1.3 Sn 0.3 O 12 .

[0087] Example 16

[0088] This example is used to illustrate the impact of using other types of hydrotalcite in the safety coating of the negative electrode.

[0089] The same process was carried out as in Example I1, except that Mg-Al-hydrotalcite was replaced by Ni-Fe-hydrotalcite with the same mass fraction.

[0090] Example 17

[0091] This embodiment is used to illustrate the impact of not adding materials capable of embedding lithium ions into the safety coating of the negative electrode.

[0092] The process is carried out with reference to Example I1, except that no material capable of inserting lithium ions is added. Specifically:

[0093] Lithium aluminum titanium phosphate was 50% by weight, polyvinylidene fluoride (PVDF) was 5% by weight, and Mg—Al hydrotalcite was 45% by weight.

[0094] Example 18

[0095] This example is used to illustrate the effect of the amount of material capable of embedding lithium ions added to the safety coating of the negative electrode. Specifically:

[0096] Example 18a:

[0097] Lithium aluminum titanium phosphate is 40% by weight, polyvinylidene fluoride (PVDF) is 5% by weight, Mg—Al hydrotalcite is 35% by weight, and graphite is 20% by weight.

[0098] Example 18b:

[0099] Lithium aluminum titanium phosphate was 35% by weight, polyvinylidene fluoride (PVDF) was 5% by weight, Mg—Al hydrotalcite was 35% by weight, and graphite was 25% by weight.

[0100] Comparative Example D1

[0101] Refer to Example I1, except that the lithium aluminum titanium phosphate is replaced by a sulfide-type lithium inorganic solid electrolyte Li3PS4 having the same mass fraction.

[0102] Comparative Example D2

[0103] Refer to Example I1, except that lithium aluminum titanium phosphate is replaced by a halide-type lithium inorganic solid electrolyte LiCl having the same mass fraction.

[0104] Comparative Example D3

[0105] Refer to Example I1, except that lithium aluminum titanium phosphate is replaced by boehmite having the same mass fraction.

[0106] Comparative Example D4

[0107] Refer to Example I1, except that lithium aluminum titanium phosphate is replaced by Al2O3 having the same mass fraction.

[0108] Example II

[0109] This Group II of Examples is used to illustrate the battery of the present invention.

[0110] The negative electrode sheets obtained from Group I of Example and Comparative Example were used to prepare batteries, specifically:

[0111] The negative electrode sheet obtained above was dried, rolled and cut into 1050*85.5mm negative electrode sheets, and then the prepared negative electrode sheet, 1070*84mm conventional positive electrode sheet and separator were wound into a roll core, and then placed in a film shell prepared by aluminum-plastic film, and the electrolyte was injected. After the steps of formation, secondary sealing, and sorting, a rectangular soft-pack lithium-ion battery with a battery capacity of approximately 4940mAh was made.

[0112] Test Case

[0113] (1) Acupuncture test

[0114] 1. Before the acupuncture test, perform 5 charge and discharge cycles using standard charge / discharge conditions, and complete the acupuncture test within 2 days after the cycle. The battery cell is fully charged and the cut-off temperature is 0.02C. The test is performed within 24 hours.

[0115] 2. Use a long conical angle steel needle with a diameter of 4mm, a cone length of 15mm, a taper of 15 degrees, and a total length of 100mm to pass through the left, center, and right sides of the battery cell (with the coding side facing down and the deep pit side facing up). The puncture positions on the left and right sides are 7.5mm±2.5mm away from the edge, the needle speed is 30mm / s, and the long conical angle steel needle remains in the battery.

[0116] 3. Test 10 cells at each location.

[0117] The batteries obtained in the examples of the present invention all passed the needle penetration test.

[0118] (2) Cyclic performance test

[0119] 1. Let stand at 25℃±2℃ for 10 minutes;

[0120] 2. Charge at 1.2C to 4.3V, then switch to 0.8C to 4.45V, cut off at 0.05C;

[0121] 3.Stand at 25℃±2℃ for 10 minutes;

[0122] 4. Discharge at 0.5C to 3V and let it stand for 10 minutes;

[0123] 5. Charge at 1.2C to 4.3V, then switch to 0.8C to 4.45V, cut off at 0.05C, and let it rest for 10 minutes;

[0124] Repeat steps 4 and 5 800 times.

[0125] (3) Rate performance test

[0126] 1.25℃±2℃ for 10min;

[0127] 2.0.2C discharge to 3V;

[0128] 3. Let it stand for 10 minutes;

[0129] 4. Charging at a certain rate (1C / 2C / 3C), with a cut-off current of 0.025C;

[0130] 5. Let it stand for 10 minutes;

[0131] 6. 0.2C discharge to 3V;

[0132] 7. Let it stand for 10 minutes;

[0133] Repeat steps 4-7 until all rate charge tests are completed.

[0134] The results of the above cycle performance test and rate performance test are recorded in Table 1.

[0135] Table 1

[0136] Capacity retention rate after 800 cycles (%) Magnification (1C / 2C / 3C) Example III 86.0 84.1 / 66.5 / 49.8 Example II2 86.3 84.3 / 66.8 / 49.9 Example II3 86.0 84.5 / 67.0 / 50.1 Example II4a 77.1 76.3 / 58.7 / 41.0 Example II4b 85.3 84.6 / 67.2 / 50.7 Example II5a 86.2 84.0 / 66.2 / 49.4 Example II5b 86.5 84.7 / 66.6 / 50.0 Example II5c 86.0 84.9 / 66.9 / 50.2 Example II6 85.9 84.3 / 66.4 / 49.6 Example II7 82.5 81.3 / 64.0 / 46.7 Example II8a 86.8 84.3 / 66.8 / 50.2 Example II8b 86.8 84.7 / 67.0 / 50.4 Comparative Example D1 77.8 76.3 / 57.6 / 40.3 Comparative Example D2 78.2 76.9 / 58.5 / 41.2 Comparative Example D3 75.3 74.1 / 55.5 / 39.2 Comparative Example D4 74.3 73.7 / 54.2 / 38.7

[0137] As can be seen from Table 1, the battery prepared with the negative electrode sheet of the present invention has significantly improved capacity retention and rate after 800 cycles compared with the control example, which significantly improves the safety performance and electrochemical performance of the battery while ensuring safety performance.

[0138] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A negative electrode plate, characterized in that: The negative electrode plate includes a current collector, a negative electrode active layer and a safety coating, wherein the negative electrode active layer is arranged on one side or both sides of the current collector, and the safety coating is arranged on the outer surface of the negative electrode active layer. The safety coating includes a lithium inorganic solid electrolyte, a binder and a flame retardant. The lithium inorganic solid electrolyte is an oxide-type lithium inorganic solid electrolyte. Based on the total weight of the safety coating, the content of the oxide-type lithium inorganic solid electrolyte is 5-80 weight%; the mass ratio of the oxide-type lithium inorganic solid electrolyte to the flame retardant is 1:(0.8-1.3); the oxide-type lithium inorganic solid electrolyte is selected from at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium aluminum silicon oxide, lithium aluminum titanium phosphorus oxide, lithium titanium aluminum phosphate and their modified dopants; the safety coating also includes a material that can be embedded in lithium ions, and the material that can be embedded in lithium ions is selected from at least one of graphite, amorphous carbon, hard carbon and silicon; based on the total weight of the safety coating, the content of the material that can be embedded in lithium ions is 15-25 weight%.

2. The negative electrode sheet according to claim 1, wherein: Based on the total weight of the safety coating, the content of the oxide-type lithium inorganic solid electrolyte is 35-45% by weight.

3. The negative electrode sheet according to claim 2, wherein: The modified dopants are selected from at least one of Ga-doped lithium lanthanum zirconium oxide, Nb-doped lithium lanthanum zirconium oxide, Ga and Nb co-doped lithium lanthanum zirconium oxide, and Sn-doped lithium lanthanum zirconium oxide.

4. The negative electrode sheet according to claim 1, wherein: Based on the total weight of the safety coating, the content of the binder is 1-5 weight %; and / or, The binder is selected from at least one of acrylic acid-modified copolymerized polyvinylidene fluoride, polyvinylidene fluoride, styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyethylene, acrylic acid and carboxymethyl cellulose.

5. The negative electrode sheet according to claim 1, wherein: Based on the total weight of the safety coating, the content of the flame retardant is 5-80 wt%; and / or, The flame retardant is selected from at least one of layered double metal hydroxides.

6. The negative electrode sheet according to claim 1, wherein: The thickness of the safety coating is 1-40 μm.

7. A battery, characterized in that: The battery includes a negative electrode plate, which is the negative electrode plate according to any one of claims 1 to 6.

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