A high energy density lithium ion battery and preparation method thereof

Abstract

The present invention belongs to the field of battery technology, and in particular, relates to a high energy density lithium ion battery, comprising a positive electrode, a separator, an electrolyte and a negative electrode current collector; the positive electrode comprises a positive electrode current collector, a positive electrode active material layer and a coating layer coated on the surface of the positive electrode active material layer, the coating layer is a sodium ion coating and / or a potassium ion coating; the electrolyte comprises a solvent and a solute, the solute comprises a lithium salt and other salts, the other salts are potassium salts and / or sodium salts; the negative electrode current collector is an aluminum foil. Compared with the prior art, the present invention has at least the following beneficial effects: first, reducing the production cost of the negative electrode of the lithium ion battery; second, increasing the energy density of the lithium ion battery; third, improving the safety performance of the lithium ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a high energy density lithium ion battery and a preparation method thereof. Background Art

[0002] In the lithium battery industry, the mainstream negative electrode current collector is copper foil, but copper foil has its limitations. First, although copper foil has good conductivity, it still has certain limitations compared with some other materials. Secondly, the copper foil is heavy, which will have a certain impact on the weight of the battery. This may make the battery heavier, which is not conducive to improving the battery energy density. Thirdly, the cost of copper foil is high, accounting for a considerable part of the material cost of the battery. Therefore, the use of copper foil will increase the total cost of the battery, which is not conducive to large-scale application and promotion.

[0003] Compared with copper foil, aluminum foil is lighter, which is beneficial to improving the energy density of the battery. In addition, the price of aluminum foil is lower than that of copper foil, which has more cost advantages.

[0004] However, aluminum foil cannot be used as negative electrode current collector on a large scale in lithium-ion battery negative electrode, because aluminum foil as negative electrode current collector will react with lithium to form lithium-aluminum alloy, resulting in a decrease in battery energy density and performance. Aluminum foil and its oxide will also form a very dense passivation film on the negative electrode surface, causing an increase in the internal resistance of the battery and affecting battery performance.

[0005] In view of this, the present invention aims to provide a high energy density lithium ion battery and a preparation method thereof, which can reduce costs and improve the energy density of the battery while ensuring battery performance through ingenious structural design and ingenious preparation method. Summary of the invention

[0006] One of the purposes of the present invention is to provide a high energy density lithium ion battery, which can reduce the cost, improve the energy density of the battery, and at the same time ensure the battery performance.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A high energy density lithium ion battery, comprising a positive electrode, a separator, an electrolyte and a negative electrode current collector;

[0009] The positive electrode comprises a positive electrode current collector, a positive electrode active material layer and a coating layer coated on the surface of the positive electrode active material layer, wherein the coating layer is a sodium ion coating and / or a potassium ion coating;

[0010] The electrolyte comprises a solvent and a solute, wherein the solute comprises a lithium salt and other salts, and the other salts are potassium salts and / or sodium salts;

[0011] The negative electrode current collector is aluminum foil.

[0012] As an improvement of the high energy density lithium ion battery of the present invention, the sodium ion coating is at least one of layered oxides, Prussians and polyanion compounds containing sodium ions; the potassium ion coating is at least one of potassium cobaltate, potassium nickelate, potassium manganate and potassium iron phosphate.

[0013] As an improvement of the high energy density lithium ion battery of the present invention, the layered oxide containing sodium ions is NaNiO2, NaMnO2, NaCoO2 and Na(Fe x Ni y Mn 1-x-y )O2, wherein 0<x<1, 0<y<1, 0<1-xy<1; the sodium ion-containing Prussian is at least one of NaFe[Fe(CN)6], Na2Fe[Fe(CN)6] and Na2Mn[Mn(CN)6]; the sodium ion-containing polyanion compound is at least one of NaFePO4, Na2FeP2O7, NaFe(SO4)2, Na3V2(PO4)3 and Na3V2(PO4)2F3.

[0014] As an improvement of the high energy density lithium ion battery of the present invention, the active material in the positive electrode active material layer is LiCoO2, LiNi x Co y Mn 1-x-y O2, LiFePO4, LiMn2O4, LiNiCoAlO2, Li4Ti5O 12 , Li2MnO3, wherein 0<x<1, 0<y<1, 0<1-xy<1.

[0015] As an improvement of the high energy density lithium ion battery of the present invention, based on the total weight of the positive electrode active material layer and the coating layer, the coating layer accounts for 0.1%-50% of the total weight.

[0016] As an improvement of the high energy density lithium ion battery of the present invention, the sodium salt is at least one of NaPF6, NaClO4 and NaBF4, and the potassium salt is at least one of KBF4, KClO4 and KPF6.

[0017] As an improvement of the high energy density lithium ion battery of the present invention, the weight ratio of the other salt to the lithium salt is (0.1-50):100.

[0018] As an improvement of the high energy density lithium ion battery of the present invention, the solvent is at least one of PC, EC, DMC, DEC and EMC.

[0019] As an improvement of the high energy density lithium ion battery of the present invention, the lithium salt is at least one of LiPF6, LiClO4, LiBF4 and LiAsF6.

[0020] Compared with the prior art, the present invention ingeniously solves the technical problem that aluminum foil cannot be used on a large scale as a negative electrode current collector, by coating a sodium ion coating or a potassium ion coating on the surface of the negative electrode, and adding potassium salt or sodium salt to the electrolyte. Since the E0 (A+ / A) of the standard hydrogen electrode (SHE) of potassium ions and sodium ions is higher than the E0 (A+ / A) of the standard hydrogen electrode potential (SHE) of lithium ions, wherein the standard hydrogen electrode potentials of potassium ions, sodium ions and lithium ions are -2.93V, -2.71V and -3.04V, respectively, during the first deposition, sodium ions or potassium ions will be deposited on the surface of the aluminum foil before lithium, and since the sodium ion coating layer and / or the potassium ion coating layer are on the outermost layer of the positive electrode sheet and react first, after the sodium ions and / or potassium ions are deposited on the surface of the aluminum foil, as a protective layer, the reaction of lithium with the aluminum foil can be prevented, so that the aluminum foil can be used as a negative electrode current collector. Using aluminum foil as the negative electrode current collector is not only low-cost, but also because aluminum foil is stronger, it can improve the mass energy density of the battery.

[0021] The entire battery adopts a negative electrode-free design. Since the processing and assembly process of the negative electrode material is omitted, the limitations of the negative electrode material in traditional lithium batteries are eliminated, thereby improving the energy density and performance of the battery, and reducing the internal resistance of the battery, thereby improving the battery's charge and discharge performance. At the same time, it can directly transfer ions between the positive and negative electrodes, thereby shortening the charging time, increasing the charging speed, and reducing the adverse reactions caused by the negative electrode material, thereby improving the safety of the battery.

[0022] Another object of the present invention is to provide a method for preparing the high energy density lithium ion battery, comprising at least the following steps:

[0023] In the first step, the positive electrode, the separator and the negative electrode current collector are assembled together by winding or laminating;

[0024] The second step is to package and inject liquid to make a finished battery;

[0025] The third step is formation. During the charging process, when the voltage is below 3V, sodium ions and / or potassium ions first come out of the positive electrode and are deposited on the aluminum foil to form a dense layer of sodium ions and / or potassium ions. In the subsequent charging process, lithium ions are deposited on the surface of the sodium ion and / or potassium ion layer. During the discharge process, the discharge capacity is set to 50-99% SOC, so that lithium ions are still deposited on the surface of the sodium / potassium ions, so that the sodium / potassium ions are still deposited on the surface of the negative electrode current collector, so that they do not participate in the discharge process, and can still play the role of isolating lithium ions and the negative electrode current collector in the subsequent charging and discharging process.

[0026] Compared with the prior art, the present invention uses a clever design. The battery uses a negative electrode-free technology (aluminum foil, porous foil, composite foil can be used as the negative electrode, and the foil is not coated with a negative electrode material). Sodium ions and potassium ions do not react with the aluminum foil, and compared with lithium ions, they have a lower charge and discharge lower limit voltage (sodium ion battery 2-4V, potassium ion battery 1.5-4V, most lithium ion batteries are 3-4.2V, and some have a higher upper limit voltage). Therefore, during the charging process, when the voltage is below 3V, lithium ions and sodium / potassium ions first come out of the positive electrode and are deposited on the aluminum foil to form a dense sodium / potassium ion layer. In the subsequent charging process, lithium ions are deposited on the surface of the sodium / potassium ions to prevent lithium ions from reacting with the aluminum foil to form a lithium-aluminum alloy, that is, this layer can play a role in isolating lithium ions and the negative electrode current collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present invention.

[0028] Figure 2 Schematic diagram of the structure of the negative electrode surface in the present invention. DETAILED DESCRIPTION

[0029] In order to further explain the technical content of the present invention, specific embodiments are used for illustration, but the protection scope of the present invention is not limited thereto. The changes or modifications of the technical solutions made by relevant personnel in the technical field according to the main concept of the present invention should be included in the protection scope of the present invention. In other words, many specific details are explained in the following description to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited by the specific implementation methods disclosed below.

[0030] The chemical reagents described in the following examples can be purchased through commercial channels or prepared by existing preparation methods; the instruments and equipment used are all existing conventional equipment; the experimental methods described are all conventional methods unless otherwise specified.

[0031] Example 1

[0032] like Figure 1 As shown, this embodiment provides a high energy density lithium ion battery, including a positive electrode 1, a separator 2, an electrolyte and a negative electrode current collector 3;

[0033] The positive electrode 1 includes a positive electrode current collector 11, a positive electrode active material layer 12 and a coating layer 13 coated on the surface of the positive electrode active material layer 12, wherein the coating layer 13 is a sodium ion coating, namely, a NaNiO2 coating; the positive electrode active material is LiCoO2, and based on the total weight of the positive electrode active material layer and the coating layer, the coating layer accounts for 10% of the total weight.

[0034] The electrolyte includes a solvent and a solute, wherein the solute includes a lithium salt LiPF6 and a sodium salt NaPF6, wherein the weight ratio of the sodium salt to the lithium salt is 10:100. The solvent includes PC, EC and DMC in a volume ratio of 4:4:2.

[0035] The negative electrode current collector 3 is aluminum foil.

[0036] The preparation method thereof comprises at least the following steps:

[0037] In the first step, the positive electrode, the separator and the negative electrode current collector are assembled together by winding or laminating;

[0038] The second step is to package and inject liquid to make a finished battery;

[0039] The third step is formation. During the charging process, when the voltage is below 3V, sodium ions first come out of the positive electrode and deposit on the aluminum foil to form a dense sodium ion layer. During the subsequent charging process, lithium ions are deposited on the surface of the sodium ion layer (such as Figure 2 As shown), during the discharge process, the discharge capacity is set to 50-99% SOC, so that lithium ions are still deposited on the surface of the sodium ions, so that the sodium ions are still deposited on the surface of the negative electrode collector, so that they do not participate in the discharge process, and can still play the role of isolating lithium ions and the negative electrode collector in the subsequent charge and discharge process.

[0040] Example 2

[0041] like Figure 1 As shown, this embodiment provides a high energy density lithium ion battery, including a positive electrode 1, a separator 2, an electrolyte and a negative electrode current collector 3;

[0042] The positive electrode 1 includes a positive electrode current collector 11, a positive electrode active material layer 12 and a coating layer 13 coated on the surface of the positive electrode active material layer 12, wherein the coating layer 13 is a potassium ion coating, namely a potassium cobalt lithium oxide coating; the positive electrode active material is lithium nickel cobalt manganese oxide, and based on the total weight of the positive electrode active material layer and the coating layer, the coating layer accounts for 15% of the total weight.

[0043] The electrolyte includes a solvent and a solute, wherein the solute includes a lithium salt LiPF6 and a potassium salt KPF6, wherein the weight ratio of the potassium salt to the lithium salt is 15:100. The solvent includes PC, EC and DEC in a volume ratio of 3:3:4.

[0044] The negative electrode current collector 3 is aluminum foil.

[0045] The preparation method thereof comprises at least the following steps:

[0046] In the first step, the positive electrode, the separator and the negative electrode current collector are assembled together by winding or laminating;

[0047] The second step is to package and inject liquid to make a finished battery;

[0048] The third step is formation. During the charging process, when the voltage is below 3V, potassium ions first come out of the positive electrode and deposit on the aluminum foil to form a dense potassium ion layer. During the subsequent charging process, lithium ions are deposited on the surface of the potassium ion layer (such as Figure 2 As shown), during the discharge process, the discharge capacity is set to 50-99% SOC, so that lithium ions are still deposited on the surface of the potassium ions, so that the potassium ions are still deposited on the surface of the negative electrode collector, so that they do not participate in the discharge process, and can still play the role of isolating lithium ions and the negative electrode collector in the subsequent charge and discharge process.

[0049] Example 3

[0050] like Figure 1 As shown, this embodiment provides a high energy density lithium ion battery, including a positive electrode 1, a separator 2, an electrolyte and a negative electrode current collector 3;

[0051] The positive electrode 1 includes a positive electrode current collector 11, a positive electrode active material layer 12 and a coating layer 13 coated on the surface of the positive electrode active material layer 12, wherein the coating layer 13 is a potassium ion coating, i.e., a lithium potassium nickelate coating; the positive electrode active material is lithium iron phosphate, and based on the total weight of the positive electrode active material layer and the coating layer, the coating layer accounts for 5% of the total weight.

[0052] The electrolyte includes a solvent and a solute, wherein the solute includes a lithium salt LiBF4 and a potassium salt KBF4, wherein the weight ratio of the potassium salt to the lithium salt is 5:100. The solvent includes PC, EMC and DEC in a volume ratio of 3:3:4.

[0053] The negative electrode current collector 3 is aluminum foil.

[0054] The preparation method thereof comprises at least the following steps:

[0055] In the first step, the positive electrode, the separator and the negative electrode current collector are assembled together by winding or laminating;

[0056] The second step is to package and inject liquid to make a finished battery;

[0057] The third step is formation. During the charging process, when the voltage is below 3V, potassium ions first come out of the positive electrode and deposit on the aluminum foil to form a dense potassium ion layer. During the subsequent charging process, lithium ions are deposited on the surface of the potassium ion layer (such as Figure 2As shown), during the discharge process, the discharge capacity is set to 50-99% SOC, so that lithium ions are still deposited on the surface of the potassium ions, so that the potassium ions are still deposited on the surface of the negative electrode collector, so that they do not participate in the discharge process, and can still play the role of isolating lithium ions and the negative electrode collector in the subsequent charge and discharge process.

[0058] Example 4

[0059] like Figure 1 As shown, this embodiment provides a high energy density lithium ion battery, including a positive electrode 1, a separator 2, an electrolyte and a negative electrode current collector 3;

[0060] The positive electrode 1 includes a positive electrode current collector 11, a positive electrode active material layer 12 and a coating layer 13 coated on the surface of the positive electrode active material layer 12, wherein the coating layer 13 is a potassium ion coating, namely a potassium iron phosphate coating; the positive electrode active material is lithium manganate, and based on the total weight of the positive electrode active material layer and the coating layer, the coating layer accounts for 8% of the total weight.

[0061] The electrolyte includes a solvent and a solute, wherein the solute includes a lithium salt LiClO4 and a potassium salt KClO4, wherein the weight ratio of the potassium salt to the lithium salt is 8:100. The solvent includes PC, DMC and DEC in a volume ratio of 2:4:4.

[0062] The negative electrode current collector 3 is aluminum foil.

[0063] The preparation method thereof comprises at least the following steps:

[0064] In the first step, the positive electrode, the separator and the negative electrode current collector are assembled together by winding or laminating;

[0065] The second step is to package and inject liquid to make a finished battery;

[0066] The third step is formation. During the charging process, when the voltage is below 3V, potassium ions first come out of the positive electrode and deposit on the aluminum foil to form a dense potassium ion layer. During the subsequent charging process, lithium ions are deposited on the surface of the potassium ion layer (such as Figure 2 As shown), during the discharge process, the discharge capacity is set to 50-99% SOC, so that lithium ions are still deposited on the surface of the potassium ions, so that the potassium ions are still deposited on the surface of the negative electrode collector, so that they do not participate in the discharge process, and can still play the role of isolating lithium ions and the negative electrode collector in the subsequent charge and discharge process.

[0067] Example 5

[0068] like Figure 1 As shown, this embodiment provides a high energy density lithium ion battery, including a positive electrode 1, a separator 2, an electrolyte and a negative electrode current collector 3;

[0069] The positive electrode 1 includes a positive electrode current collector 11, a positive electrode active material layer 12 and a coating layer 13 coated on the surface of the positive electrode active material layer 12, wherein the coating layer 13 is a sodium ion coating, namely, a NaFe[Fe(CN)6] coating; the positive electrode active material is lithium nickel cobalt aluminum oxide, and based on the total weight of the positive electrode active material layer and the coating layer, the coating layer accounts for 35% of the total weight.

[0070] The electrolyte includes a solvent and a solute, wherein the solute includes a lithium salt LiAsF6 and a sodium salt NaClO4, wherein the weight ratio of the sodium salt to the lithium salt is 35:100. The solvent includes EC, DMC and DEC in a volume ratio of 2:4:4.

[0071] The negative electrode current collector 3 is aluminum foil.

[0072] The preparation method thereof comprises at least the following steps:

[0073] In the first step, the positive electrode, the separator and the negative electrode current collector are assembled together by winding or laminating;

[0074] The second step is to package and inject liquid to make a finished battery;

[0075] The third step is formation. During the charging process, when the voltage is below 3V, sodium ions first come out of the positive electrode and deposit on the aluminum foil to form a dense sodium ion layer. During the subsequent charging process, lithium ions are deposited on the surface of the sodium ion layer (such as Figure 2 As shown), during the discharge process, the discharge capacity is set to 50-99% SOC, so that lithium ions are still deposited on the surface of the sodium ions, so that the sodium ions are still deposited on the surface of the negative electrode collector, so that they do not participate in the discharge process, and can still play the role of isolating lithium ions and the negative electrode collector in the subsequent charge and discharge process.

[0076] Example 6

[0077] like Figure 1 As shown, this embodiment provides a high energy density lithium ion battery, including a positive electrode 1, a separator 2, an electrolyte and a negative electrode current collector 3;

[0078] The positive electrode 1 includes a positive electrode current collector 11, a positive electrode active material layer 12 and a coating layer 13 coated on the surface of the positive electrode active material layer 12, wherein the coating layer 13 is a sodium ion coating, namely, a NaFePO4 coating; the positive electrode active material is lithium cobalt oxide, and based on the total weight of the positive electrode active material layer and the coating layer, the coating layer accounts for 35% of the total weight.

[0079] The electrolyte includes a solvent and a solute, wherein the solute includes a lithium salt LiPF6 and a sodium salt NaBF4, wherein the weight ratio of the sodium salt to the lithium salt is 12:100. The solvent includes PC, DMC and DEC in a volume ratio of 2:4:4.

[0080] The negative electrode current collector 3 is aluminum foil.

[0081] The preparation method thereof comprises at least the following steps:

[0082] In the first step, the positive electrode, the separator and the negative electrode current collector are assembled together by winding or laminating;

[0083] The second step is to package and inject liquid to make a finished battery;

[0084] The third step is formation. During the charging process, when the voltage is below 3V, sodium ions first come out of the positive electrode and deposit on the aluminum foil to form a dense sodium ion layer. During the subsequent charging process, lithium ions are deposited on the surface of the sodium ion layer (such as Figure 2 As shown), during the discharge process, the discharge capacity is set to 50-99% SOC, so that lithium ions are still deposited on the surface of the sodium ions, so that the sodium ions are still deposited on the surface of the negative electrode collector, so that they do not participate in the discharge process, and can still play the role of isolating lithium ions and the negative electrode collector in the subsequent charge and discharge process.

[0085] Example 7

[0086] Different from Example 1, the sodium ion coating is specifically a NaMnO2 coating, and the positive electrode active material is Li4Ti5O 12 The rest is the same as in Example 1 and will not be described again here.

[0087] Example 8

[0088] The difference from Example 5 is that the sodium ion coating is specifically a Na2Mn[Mn(CN)6] coating, the positive electrode active material is LiNiCoAlO2, and the rest is the same as Example 5 and will not be repeated here.

[0089] Example 9

[0090] The difference from Example 6 is that the sodium ion coating is specifically a Na3V2(PO4)2F3 coating, and the positive electrode active material is Li2MnO3. The rest is the same as Example 6 and will not be repeated here.

[0091] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A high energy density lithium ion battery, characterized in that: It includes a positive electrode, a separator, an electrolyte and a negative electrode current collector; The positive electrode comprises a positive electrode current collector, a positive electrode active material layer and a coating layer coated on the surface of the positive electrode active material layer, wherein the coating layer is a sodium ion coating and / or a potassium ion coating; The electrolyte comprises a solvent and a solute, wherein the solute comprises a lithium salt and other salts, and the other salts are potassium salts and / or sodium salts; The negative electrode current collector is aluminum foil; The preparation method thereof comprises at least the following steps: In the first step, the positive electrode, the separator and the negative electrode current collector are assembled together by winding or laminating; The second step is to package and inject liquid to make a finished battery; The third step is formation. During the charging process, when the voltage is below 3V, sodium ions and / or potassium ions first come out of the positive electrode and are deposited on the aluminum foil to form a dense layer of sodium ions and / or potassium ions. In the subsequent charging process, lithium ions are deposited on the surface of the sodium ion and / or potassium ion layer. During the discharge process, the discharge capacity is set to 50-99% SOC, so that lithium ions are still deposited on the surface of the sodium / potassium ions, so that the sodium / potassium ions are still deposited on the surface of the negative electrode current collector, so that they do not participate in the discharge process, and can still play the role of isolating lithium ions and the negative electrode current collector in the subsequent charging and discharging process.

2. The high energy density lithium ion battery according to claim 1, characterized in that: The sodium ion coating is at least one of layered oxides, Prussian oxides and polyanion compounds containing sodium ions; the potassium ion coating is at least one of potassium cobaltate, potassium nickelate, potassium manganate and potassium iron phosphate.

3. The high energy density lithium ion battery according to claim 2, characterized in that: The layered oxides containing sodium ions are NaNiO2, NaMnO2, NaCoO2 and Na(Fe x Ni y Mn 1-x-y )O2, wherein 0<x<1, 0<y<1, 0<1-xy<1; the sodium ion-containing Prussian is at least one of NaFe[Fe(CN)6], Na2Fe[Fe(CN)6] and Na2Mn[Mn(CN)6]; the sodium ion-containing polyanion compound is at least one of NaFePO4, Na2FeP2O7, NaFe(SO4)2, Na3V2(PO4)3 and Na3V2(PO4)2F3.

4. The high energy density lithium ion battery according to claim 1, characterized in that: The active material in the positive electrode active material layer is LiCoO2, LiNi x Co y Mn 1-x-y O2, LiFePO4, LiMn2O4, LiNiCoAlO2, Li4Ti5O 12 , Li2MnO3, wherein 0<x<1, 0<y<1, 0<1-xy<1.

5. The high energy density lithium ion battery according to claim 1, characterized in that: Based on the total weight of the positive electrode active material layer and the coating layer, the coating layer accounts for 0.1%-50% of the total weight.

6. The high energy density lithium ion battery according to claim 1, characterized in that: The sodium salt is at least one of NaPF6, NaClO4 and NaBF4, and the potassium salt is at least one of KBF4, KClO4 and KPF6.

7. The high energy density lithium ion battery according to claim 1, characterized in that: The weight ratio of the other salt to the lithium salt is (0.1-50):

100.

8. The high energy density lithium ion battery according to claim 1, characterized in that: The solvent is at least one of PC, EC, DMC, DEC and EMC.

9. The high energy density lithium ion battery according to claim 1, characterized in that: The lithium salt is at least one of LiPF6, LiClO4, LiBF4 and LiAsF6.

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