A positive electrode sheet, a method for manufacturing the same, and a solid-state lithium battery

Abstract

The application discloses a positive electrode sheet, a preparation method thereof and a solid-state lithium battery. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector. The positive electrode active material layer comprises a positive electrode active material, a positive electrode conductive agent and a positive electrode binder. The positive electrode active material comprises a ternary material and lithium manganese iron phosphate and a functional solid-state electrolyte which are sequentially coated on the surface of the ternary material from inside to outside. The solid-state lithium battery prepared from the positive electrode sheet has the advantages of high energy density, large-current charging and discharging, safety and reliability, long charging and discharging life, simple preparation process and easy scale production.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology. Specifically, this invention relates to a positive electrode sheet, its preparation method, and a solid-state lithium battery. Background Technology

[0002] Amidst the global emphasis on climate change and energy conservation and carbon reduction, the new energy industry has become one of the strategic emerging industries of the new century. As a crucial technological support for the new energy industry, novel energy storage battery technology has garnered significant attention. With the rapid development of electrification in low-altitude aircraft and transportation, the demands for high-energy-density batteries that also possess high current charging and discharging capabilities and high safety are increasing. In recent years, advancements in high-capacity ternary cathode materials and silicon-based anode materials have pushed the energy density of lithium-ion batteries based on liquid organic electrolytes to over 240Wh / kg, thereby significantly improving driving range and time. However, relying solely on ternary cathode materials to increase battery energy density also brings significant safety hazards, such as the risk of fire and explosion under certain operating conditions (e.g., needle penetration). Furthermore, to achieve high energy density, the cathode or anode slurry typically has a high loading on the current collector. This increases the lithium-ion diffusion distance, degrades diffusion performance, and reduces high-current charging and discharging capabilities. In applications such as low-altitude aircraft and transportation, the battery is prone to overheating, potentially leading to thermal runaway.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention provide a positive electrode sheet, a method for preparing the same, and a solid-state lithium battery.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, embodiments of the present invention provide a positive electrode sheet, comprising a positive current collector and a positive active material layer coated on the positive current collector; the positive active material layer comprises a positive active material, a positive conductive agent and a positive binder; the positive active material comprises a ternary material and lithium manganese iron phosphate and a functionalized solid electrolyte sequentially coated on the surface of the ternary material from the inside out.

[0007] In some embodiments, the functionalized solid electrolyte is Li 1+3y Ti2(P 1-y M y S 4-x Se x 3. LiM'Cl6:zMt m S nany one of them; wherein, M includes at least one of Ge, Si, and Sn, M' includes at least one of Nb and Ta, and Mt includes at least one of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn; 0 < x < 1, 0 < y < 1, 0 < z ≤ 3, and m and n satisfy the stoichiometric ratio requirements; and / or, the chemical formula of the ternary material is LiNi 1-a-b Co a Mn b O2, where 0 < a < 1 and 0 < b < 1; and / or, the weight ratio of the ternary material, the lithium iron manganese phosphate, and the functionalized solid electrolyte is 100:(10 - 50):(1 - 5).

[0008] In some embodiments, the surface density of the positive electrode active material layer coated on the positive electrode current collector is 14 - 18 mg / cm 2 .

[0009] In some embodiments, in the positive electrode active material layer, the weight ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (90 - 98):(1 - 5):(1 - 5); Optionally, the positive electrode conductive agent includes at least one of conductive carbon black, conductive graphite, graphene, carbon nanotubes, and graphitized carbon fibers; Optionally, the positive electrode binder includes at least one of polyvinylidene fluoride, acrylonitrile copolymer, hydroxypropyl methylcellulose, sodium carboxymethylcellulose, and styrene-butadiene rubber.

[0010] In a second aspect, an embodiment of the present invention further provides a method for preparing a positive electrode sheet as described in the first aspect, including the following steps: After stirring and mixing the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder, a positive electrode slurry is prepared by adding a positive electrode solvent; then the positive electrode slurry is coated on the positive electrode current collector, and after drying, rolling, cutting, and vacuum baking, the positive electrode sheet is obtained.

[0011] In a third aspect, an embodiment of the present invention further provides a solid-state lithium battery, including a housing, a positive electrode sheet, a negative electrode sheet, and a solid electrolyte membrane; the positive electrode sheet is the positive electrode sheet described in the first aspect or the positive electrode sheet prepared by the preparation method described in the second aspect.

[0012] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on the negative electrode current collector; the negative electrode active material layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder; the surface density of the negative electrode active material layer coated on the negative electrode current collector is 6 - 9 mg / cm 2 .

[0013] In some embodiments, the weight ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder in the negative electrode active material layer is (90~98):(1~5):(1~5); Optionally, the negative electrode active material includes at least one of graphite, silicon-carbon negative electrode material, and silicon-oxygen negative electrode material; Optionally, the negative electrode conductive agent includes at least one of conductive carbon black, conductive graphite, graphene, carbon nanotubes, and graphitized carbon fibers. Optionally, the negative electrode binder includes at least one of polyvinylidene fluoride, acrylonitrile copolymer, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0014] In some embodiments, the negative electrode sheet is prepared by a method comprising the following steps: mixing negative electrode active material, negative electrode conductive agent and negative electrode binder, then adding negative electrode solvent to prepare a negative electrode slurry; then coating the negative electrode slurry onto the negative electrode current collector, and then drying, rolling, cutting and vacuum baking to obtain the negative electrode sheet.

[0015] Fourthly, embodiments of the present invention also propose a method for preparing a solid-state lithium battery as described in the third aspect, comprising the following steps: Positive and negative electrode sheets are stacked alternately, and a solid electrolyte membrane is placed between adjacent positive and negative electrode sheets to form a core. The core is then dried and placed in a housing, and then pressurized and sealed to obtain the solid-state lithium battery.

[0016] The advantages and beneficial effects of the embodiments of the present invention are as follows: The embodiments of the present invention prepare positive electrode active materials by sequentially coating lithium manganese iron phosphate and functionalized solid electrolyte with high electronic and ionic conductivity on the surface of ternary materials. This can ensure the lithium ion insertion / extraction efficiency, improve the rate performance of the battery, and the resulting solid lithium battery has the advantages of high energy density, high current charging and discharging capability, safety and reliability, and long charge / discharge life. Attached Figure Description

[0017] Figure 1 This is a photograph of the solid-state lithium battery obtained in Example 1 of the present invention after a 5mm needle penetration test.

[0018] Figure 2 This is a photograph of the solid-state lithium battery prepared in Comparative Example 1 after cycling.

[0019] Figure 3 This is a photograph of the solid-state lithium battery prepared in Comparative Example 2, taken from a 5mm needle penetration test. Detailed Implementation

[0020] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] In this invention, when a value is described as a range, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as specific numerical values ​​falling within that range, regardless of whether specific numerical values ​​or specific subranges are explicitly specified.

[0022] In this invention, the terms “comprising” and “including” and their various variations mean that other elements or wholes may be included but are not specifically described.

[0023] In this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0024] In a first aspect, embodiments of the present invention provide a positive electrode sheet, comprising a positive current collector and a positive active material layer coated on the positive current collector; the positive active material layer comprises a positive active material, a positive conductive agent and a positive binder; the positive active material comprises a ternary material and lithium manganese iron phosphate and a functionalized solid electrolyte sequentially coated on the surface of the ternary material from the inside out.

[0025] In this embodiment of the invention, the positive electrode active material has a ternary material as the innermost layer, and lithium manganese iron phosphate and a functionalized solid electrolyte are sequentially coated on its surface from the inside out. The lithium manganese iron phosphate has an olivine-type crystal structure and is coated on the surface of the ternary material to form a physical barrier. This structure is highly stable during charging and discharging and is not easily decomposed even under high temperature or overcharge conditions, which significantly suppresses the risk of battery thermal runaway. Furthermore, a functionalized solid electrolyte is coated on the outer surface of the lithium manganese iron phosphate, which is beneficial for ion conduction and thus can improve the battery's high-current charging and discharging capability.

[0026] In some embodiments, the specific preparation process of the positive electrode active material is as follows: lithium manganese iron phosphate powder is first mixed with sucrose powder by ball milling (ball milling speed is 100~300 rpm, mixing time is 15~60 min); then ternary material powder is added and ball milling is continued for 30~100 min; then the resulting mixture is sintered in an inert atmosphere at 600~800℃ for 4~8 h to obtain a ternary material coated with lithium manganese iron phosphate; then, functionalized solid electrolyte is mixed with the above-mentioned ternary material coated with lithium manganese iron phosphate by ball milling, controlling the ball milling speed to be 100~300 rpm and the ball milling time to be 30~100 min, to obtain the positive electrode active material.

[0027] In some embodiments, the functionalized solid electrolyte is Li 1+3y Ti2(P 1-y M y S 4-x Se x )3, LiM’Cl6:zMt m S n any one of; wherein, M includes at least one of Ge, Si, Sn, M' includes at least one of Nb, Ta, Mt includes at least one of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn; 0 < x < 1, 0 < y < 1, 0 < z ≤ 3, m and n satisfy the stoichiometric requirements; the above functionalized solid electrolyte has high electronic, ionic and / or electrochemical activity, which is beneficial to improving the electrochemical performance of the battery; and / or, the chemical formula of the ternary material is LiNi 1-a-b Co a Mn b O2, wherein, 0 < a < 1, 0 < b < 1; and / or, the chemical formula of the lithium iron manganese phosphate is LiMn c Fe 1-c PO4 (0 < c < 1), and / or, the weight ratio of the ternary material, the lithium iron manganese phosphate and the functionalized solid electrolyte is 100:(10 - 50):(1 - 5).

[0028] In some embodiments, the surface density of the positive electrode active material layer coated on the positive electrode current collector is 14 - 18 mg / cm 2 .

[0029] In some embodiments, in the positive electrode active material layer, the weight ratio of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder is (90 - 98):(1 - 5):(1 - 5); Optionally, the positive electrode conductive agent includes at least one of conductive carbon black, conductive graphite, graphene, carbon nanotubes, graphitized carbon fibers; Optionally, the positive electrode binder includes at least one of polyvinylidene fluoride, acrylonitrile copolymer, hydroxypropyl methyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber.

[0030] Second, the embodiments of the present invention also propose a method for preparing the positive electrode sheet as described in the first aspect, including the following steps: After stirring and mixing the positive electrode active material, positive electrode conductive agent and positive electrode binder, a positive electrode solvent is added to prepare a positive electrode slurry. The positive electrode slurry is then coated onto the positive electrode current collector, and after drying, rolling, cutting and vacuum baking, the positive electrode sheet is obtained. The type of positive electrode solvent is not particularly limited, and those skilled in the art can choose it according to actual needs, such as N-methyl-2-pyrrolidone.

[0031] Thirdly, embodiments of the present invention also provide a solid-state lithium battery, comprising a casing, a positive electrode, a negative electrode, and a solid electrolyte membrane; wherein the positive electrode is the positive electrode described in the first aspect or the positive electrode prepared by the preparation method described in the second aspect.

[0032] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on the negative electrode current collector; the negative electrode active material layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder; the areal density of the negative electrode active material layer coated on the negative electrode current collector is 6~9 mg / cm³. 2 .

[0033] The embodiments of the present invention control the areal density of the positive and negative electrode active material layers coated on their respective current collectors, which can ensure high specific energy performance and improve the high current charging and discharging capability of the battery, and can meet the requirements of 3C rate charging and 6C rate discharging.

[0034] In some embodiments, the weight ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder in the negative electrode active material layer is (90~98):(1~5):(1~5); Optionally, the negative electrode active material includes at least one of graphite, silicon-carbon negative electrode material, and silicon-oxygen negative electrode material; Optionally, the negative electrode conductive agent includes at least one of conductive carbon black, conductive graphite, graphene, carbon nanotubes, and graphitized carbon fibers. Optionally, the negative electrode binder includes at least one of polyvinylidene fluoride, acrylonitrile copolymer, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0035] In some embodiments, the negative electrode sheet is prepared by a method comprising the following steps: mixing a negative electrode active material, a negative electrode conductive agent and a negative electrode binder, then adding a negative electrode solvent to prepare a negative electrode slurry; then coating the negative electrode slurry onto the negative electrode current collector, and then drying, rolling, cutting and vacuum baking to obtain the negative electrode sheet; wherein, the type of negative electrode solvent is not particularly limited, and those skilled in the art can select it according to actual needs, such as water.

[0036] Fourthly, embodiments of the present invention also propose a method for preparing a solid-state lithium battery as described in the third aspect, comprising the following steps: Positive and negative electrode sheets are stacked alternately, and a solid electrolyte membrane is placed between adjacent positive and negative electrode sheets to form a core. The core is then dried and placed in a housing, and then pressurized and sealed to obtain the solid-state lithium battery.

[0037] It should be noted that the types of positive current collectors in the positive electrode sheet and negative current collectors in the negative electrode sheet in the embodiments of the present invention are not particularly limited. Those skilled in the art can make selections according to actual needs. For example, the positive current collector can be a metal foil, such as aluminum foil; the negative current collector can also be a metal foil, such as copper foil.

[0038] Similarly, the type of solid electrolyte membrane in the solid lithium battery of the present invention is not particularly limited. Those skilled in the art can choose according to actual needs. For example, the solid electrolyte membrane can be Li6PS5Cl, Li3PS4, Li7P3S11, etc.

[0039] The following are non-limiting embodiments and comparative examples of the present invention. It should be noted that the schemes in the comparative examples are not prior art, but are only set up for comparison with the schemes in the embodiments, and are not intended to limit the present invention. Unless otherwise stated, all raw materials used in the embodiments and comparative examples are conventional commercially available products, or can be prepared by known methods; and the experimental methods in the embodiments that do not specify specific conditions are conventional methods and conditions well known in the art.

[0040] Example 1 This embodiment provides a method for preparing a solid-state lithium battery, including the following steps: (1) Cathode sheet fabrication: Among the cathode active materials, the ternary material is LiNi. 0.6 Co 0.2 Mn 0.2 O2, lithium manganese iron phosphate is LiMn 0.6 Fe 0.4 PO4, functionalized solid electrolyte is Li 1.3 Ti2(P 0.9 Ge 0.1 S 3.9 Se 0.1 3. The ternary material surface is coated with lithium manganese iron phosphate and functionalized solid electrolyte sequentially from the inside out; and LiNi 0.6 Co 0.2 Mn 0.2 O2, LiMn 0.6 Fe 0.4 PO4, Li 1.3 Ti2(P 0.9 Ge0.1 S 3.9 Se 0.1 The weight ratio of the three components is 100:25:3.

[0041] The preparation process of the above positive electrode active material is as follows: Take 25 kg of LiMn 0.6 Fe 0.4 PO4 powder and 0.5 kg of sucrose powder were mixed using a spherical mixing method at 150 rpm for 30 min; then 100 kg of LiNi was added. 0.6 Co 0.2 Mn 0.2 O2 powder was ball-milled for 60 min; then the resulting mixture was sintered at 700 °C for 6 h in an argon atmosphere to obtain LiMn. 0.6 Fe 0.4 PO4-coated LiNi 0.6 Co 0.2 Mn 0.2 O2 material; then add 3kg Li 1.3 Ti2(P 0.9 Ge 0.1 S 3.9 Se 0.1 )3 and the LiNi prepared above 0.6 Co 0.2 Mn 0.2 O2 material surface coated with LiMn 0.6 Fe 0.4 The PO4 composite material was mixed by ball milling, with the ball milling speed controlled at 200 rpm and the milling time at 60 min, to obtain the above-mentioned positive electrode active material.

[0042] Then, take 96 kg of the above-mentioned positive electrode active material, 1.5 kg of conductive carbon black, 1 kg of carbon nanotubes, and 1.5 kg of polyvinylidene fluoride, stir and mix them, and then add an appropriate amount of N-methyl-2-pyrrolidone to prepare a positive electrode slurry; then coat the positive electrode slurry onto the positive electrode current collector aluminum foil (the coating surface density is 17 mg / cm²). 2 After drying, rolling, and cutting (19.7cm×14.7cm in size), the positive electrode is finally baked under vacuum to produce a positive electrode sheet.

[0043] (2) Preparation of negative electrode sheet: Take 96.5 kg of graphite, 1 kg of conductive carbon black, 1 kg of sodium carboxymethyl cellulose, and 1.5 kg of styrene-butadiene rubber and stir them together. Then add an appropriate amount of water to make a negative electrode slurry. Then coat the negative electrode slurry onto the copper foil of the negative electrode current collector (the coating surface density is 8.01 mg / cm²). 2 After drying, rolling, and cutting (size 20.1cm×15.1cm), the negative electrode sheet is finally produced by vacuum baking.

[0044] (3) Solid-state lithium battery assembly: Take positive electrode sheet, negative electrode sheet, and Li6PS5Cl solid electrolyte membrane, and stack them in the order of negative electrode sheet / / solid electrolyte membrane / / positive electrode sheet / / solid electrolyte membrane / / negative electrode sheet / / solid electrolyte membrane / / positive electrode sheet / / solid electrolyte membrane / / negative electrode sheet / / solid electrolyte membrane / / positive electrode sheet / / solid electrolyte membrane / / negative electrode sheet ..., and the outermost two sides of the core should always be negative electrode sheet.

[0045] (4) Packaging: After vacuum drying of the core, place it in the housing, pressurize and vacuum seal it to obtain a solid lithium battery.

[0046] The solid-state lithium battery prepared in this embodiment was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.2 Ah at a 0.33C rate and a mass energy density of 240.1 Wh / kg; the ratio of the 6C rate discharge capacity to the 0.33C discharge capacity was 85.6%; the ratio of the 3C rate constant current charging capacity to (3C rate constant current charging capacity + constant voltage charging capacity) was 97.8%; after 1000 cycles of 1C rate charging and 3C rate discharging, the capacity retention rate was 85.7%; and the battery did not catch fire or explode during a 5mm needle penetration test (e.g., ...). Figure 1 (As shown).

[0047] Example 2 This embodiment is basically the same as Embodiment 1, except that: in step (1) of this embodiment, when the positive electrode sheet is made, the ternary material in the positive electrode active material is LiNi. 0.83 Co 0.12 Mn 0.05 O2, the functionalized solid electrolyte is LiTaCl6:Al2S3; and LiNi 0.83 Co 0.12 Mn 0.05 O2, LiMn 0.6 Fe 0.4 The weight ratio of PO4, LiTaCl6, and Al2S3 is 100:43:4; and the areal density of the positive electrode slurry coated on the positive electrode current collector is 16 mg / cm³. 2 In step (2), during the fabrication of the negative electrode sheet, the areal density of the negative electrode slurry coated on the negative electrode current collector is 8.64 mg / cm². 2 .

[0048] The solid-state lithium battery prepared in this embodiment was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.9 Ah at a 0.33C rate and a mass energy density of 353.8 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 84.3%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 96.3%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 84.2%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0049] Example 3 This embodiment is basically the same as Embodiment 1, except that: in step (1) of this embodiment, when the positive electrode sheet is made, the ternary material in the positive electrode active material is LiNi. 0.9 Co 0.05 Mn 0.05 O2, the functionalized solid electrolyte is LiTaCl6:1.5TiS2; and LiNi 0.9 Co 0.05 Mn 0.05 O2, LiMn 0.6 Fe 0.4 The weight ratio of PO4, LiTaCl6:1.5TiS2 is 100:50:5; and the areal density of the positive electrode slurry coated on the positive electrode current collector is 15 mg / cm³. 2 In step (2), during the fabrication of the negative electrode sheet, the areal density of the negative electrode slurry coated on the negative electrode current collector is 8.33 mg / cm². 2 .

[0050] The solid-state lithium battery prepared in this embodiment was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.8 Ah at a 0.33C rate and a mass energy density of 260.8 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 83.1%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 95.2%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 82.4%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0051] Example 4 This embodiment is basically the same as Embodiment 1, except that: in step (1) of this embodiment, when the positive electrode sheet is fabricated, the LiNi in the positive electrode active material... 0.6 Co 0.2 Mn 0.2 O2, LiMn 0.6 Fe 0.4 PO4, Li 1.3 Ti2(P0.9 Ge 0.1 S 3.9 Se 0.1 )3 The weight ratio of the three is 100:40:3.

[0052] The solid-state lithium battery prepared in this embodiment was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.6 Ah at a 0.33C rate and a mass energy density of 237.1 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 85.3%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 97.5%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 85.6%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0053] Example 5 This embodiment is basically the same as Embodiment 1, except that: in step (1) of this embodiment, when the positive electrode sheet is fabricated, the LiNi in the positive electrode active material... 0.6 Co 0.2 Mn 0.2 O2, LiMn 0.6 Fe 0.4 PO4, Li 1.3 Ti2(P 0.9 Ge 0.1 S 3.9 Se 0.1 )3 The weight ratio of the three is 100:25:5.

[0054] The solid-state lithium battery prepared in this embodiment was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.1 Ah at a 0.33C rate and a mass energy density of 238.2 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 87.1%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 98.0%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 85.9%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0055] Example 6 This embodiment is basically the same as Embodiment 1, except that: in step (2) of this embodiment, when the negative electrode sheet is made, the negative electrode active material is a mixture of 85.3 kg of graphite and 7.2 kg of silicon-carbon negative electrode material; and the areal density of the negative electrode slurry coated on the negative electrode current collector is 6.23 mg / cm². 2 .

[0056] The solid-state lithium battery prepared in this embodiment was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.2 Ah at a 0.33C rate and a mass energy density of 252.7 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 87.3%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 98.3%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 82.6%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0057] Example 7 This embodiment is basically the same as Embodiment 1, except that: in step (2) of this embodiment, when the negative electrode sheet is made, the negative electrode active material is a mixture of 83.3 kg of graphite and 9.2 kg of silicon-oxygen negative electrode material; and the areal density of the negative electrode slurry coated on the negative electrode current collector is 6.23 mg / cm². 2 .

[0058] The solid-state lithium battery prepared in this embodiment was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.2 Ah at a 0.33C rate and a mass energy density of 252.6 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 88.6%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 98.7%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 80.1%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0059] Example 8 This embodiment is basically the same as Embodiment 1, except that: in step (1) of this embodiment, when the positive electrode sheet is made, the chemical formula of lithium manganese iron phosphate in the positive electrode active material is LiMn. 0.7 Fe 0.3 PO4.

[0060] The solid-state lithium battery prepared in this embodiment was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.1 Ah at a 0.33C rate and a mass energy density of 239.4 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 83.1%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 95.3%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 83.8%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0061] Example 9 This embodiment is basically the same as embodiment 1, except that: in step (1) of this embodiment, when the positive electrode sheet is made, the functionalized solid electrolyte in the positive electrode active material is LiNbCl6:2CoS.

[0062] The solid-state lithium battery prepared in this embodiment was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.1 Ah at a 0.33C rate and a mass energy density of 239.8 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 82.1%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 95.6%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 85.4%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0063] Comparative Example 1 This comparative example is basically the same as Example 1, except that: the preparation process of the positive electrode active material in step (1) of this comparative example is: the ternary material, lithium manganese iron phosphate and functionalized solid electrolyte are directly stirred and mixed to obtain the positive electrode active material.

[0064] The solid-state lithium battery prepared in this comparative example was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.1 Ah at a 0.33C rate and a mass energy density of 239.5 Wh / kg; the ratio of the 6C rate discharge capacity to the 0.33C discharge capacity was 80.3%; the ratio of the 3C rate constant current charging capacity to (3C rate constant current charging capacity + constant voltage charging capacity) was 94.2%; after 1000 cycles of 1C rate charging and 3C rate discharging, the capacity retention rate was 78.6%, and the battery exhibited bulging (e.g., ...). Figure 2 (As shown); it did not catch fire or explode during a 5mm needle puncture test.

[0065] Therefore, compared with the method of sequentially coating lithium manganese iron phosphate and functionalized solid electrolyte on the surface of ternary materials in the embodiments of the present invention, the method of direct stirring and mixing cannot guarantee battery safety.

[0066] Comparative Example 2 This comparative example is basically the same as Example 1, except that: in step (1) of this comparative example, when the positive electrode sheet is made, the surface of the ternary material in the positive electrode active material is not coated with lithium manganese iron phosphate (LiMn). 0.6 Fe 0.4 PO4.

[0067] The solid-state lithium battery prepared in this comparative example was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.9 Ah at a 0.33C rate and a mass energy density of 242.5 Wh / kg; the ratio of the 6C rate discharge capacity to the 0.33C discharge capacity was 85.9%; the ratio of the 3C rate constant current charging capacity to (3C rate constant current charging capacity + constant voltage charging capacity) was 97.9%; after 1000 cycles of 1C rate charging and 3C rate discharging, the capacity retention rate was 83.1%; and the battery did not catch fire or explode (e.g., after a 5mm needle penetration test) Figure 3 (As shown).

[0068] Therefore, it is evident that without coating the surface of ternary materials with lithium manganese iron phosphate, battery safety cannot be guaranteed.

[0069] Comparative Example 3 This comparative example is basically the same as Example 1, except that: in step (1) of this comparative example, when the positive electrode sheet is made, the surface of the ternary material in the positive electrode active material is not coated with functionalized solid electrolyte Li. 1.3 Ti2(P 0.9 Ge 0.1 S 3.9 Se 0.1 3.

[0070] The solid-state lithium battery prepared in this comparative example was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.9 Ah at a 0.33C rate and a mass energy density of 242.5 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 78.3%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 92.1%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 75.9%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0071] It is evident that if the surface of ternary materials is not coated with functionalized solid electrolyte, the high-current charge-discharge performance and cycle performance of the battery will deteriorate.

[0072] Comparative Example 4 This comparative example is basically the same as Example 1, except that: in step (1) of this comparative example, when the positive electrode sheet is made, the LiNi in the positive electrode active material is... 0.6 Co 0.2 Mn 0.2 O2, LiMn 0.6 Fe 0.4 PO4, Li 1.3 Ti2(P 0.9 Ge 0.1 S 3.9 Se0.1 )3 The weight ratio of the three is 100:25:10.

[0073] The solid-state lithium battery prepared in this comparative example was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.1 Ah at a 0.33C rate and a mass energy density of 235.2 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 87.8%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 98.2%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 85.5%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0074] Therefore, if the mass ratio of functionalized solid electrolytes coated on the surface of ternary materials is too large, although the rate performance is improved, the energy density of the battery will decrease because the solid electrolyte itself does not exert its capacity.

[0075] Comparative Example 5 This comparative example is basically the same as Example 1, except that: in step (1) of this comparative example, when the positive electrode sheet is made, the LiNi in the positive electrode active material is... 0.6 Co 0.2 Mn 0.2 O2, LiMn 0.6 Fe 0.4 PO4, Li 1.3 Ti2(P 0.9 Ge 0.1 S 3.9 Se 0.1 )3 The weight ratio of the three is 100:60:3.

[0076] The solid-state lithium battery prepared in this comparative example was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.1 Ah at a 0.33C rate and a mass energy density of 228.1 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 78.6%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 91.6%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 84.3%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0077] This shows that when the surface of the ternary material is coated with LiMn 0.6 Fe 0.4 When the mass proportion of PO4 increases, although the safety performance of the battery is not affected, the energy density and rate performance of the battery deteriorate.

[0078] Comparative Example 6 This comparative example is basically the same as Example 1, except that: in step (1) of this comparative example, when the positive electrode sheet is made, the areal density of the positive electrode slurry coated on the positive electrode current collector is 12 mg / cm². 2 Furthermore, in step (2), the surface density of the negative electrode slurry coating on the negative electrode current collector is 5.65 mg / cm³. 2 .

[0079] The solid-state lithium battery prepared in this comparative example was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.1 Ah at a 0.33C rate and a mass energy density of 230.2 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 87.1%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 98.6%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 87.5%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0080] It can be seen that when the coating amount of positive and negative electrode slurries on the corresponding current collectors decreases, it will affect the energy density of the battery. However, at the same time, due to the reduction in coating amount, the diffusion of ions on the electrode is improved, and the high-current charge-discharge and cycle performance are enhanced.

[0081] Comparative Example 7 This comparative example is basically the same as Example 1, except that: in step (1) of this comparative example, when the positive electrode sheet is made, the areal density of the positive electrode slurry coated on the positive electrode current collector is 20 mg / cm³. 2 Furthermore, in step (2), the surface density of the negative electrode slurry coating on the negative electrode current collector is 9.43 mg / cm³. 2 .

[0082] The solid-state lithium battery prepared in this comparative example was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 56.2 Ah at a 0.33C rate and a mass energy density of 245.1 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 78.6%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 93.5%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 76.9%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0083] It can be seen that when the coating amount of positive and negative electrode slurries on the corresponding current collectors is increased, although the energy density is improved, the diffusion performance of ions on the electrode will be worse due to the increased coating amount, and the high current charge-discharge and cycle performance will be correspondingly worse.

[0084] Comparative Example 8 This comparative example is basically the same as Example 1, except that: in step (1) of this comparative example, when the positive electrode sheet is made, the ternary material LiNi is used in the positive electrode active material. 0.6 Co 0.2 Mn 0.2 The surface of O2 is sequentially coated from the inside out with Al2O3 nanoparticles (300nm particle size) and LiMn. 0.6 Fe 0.4 PO4 and Li 1.3 Al 0.3 Ti 1.7 (PO4)3, and LiNi 0.6 Co 0.2 Mn 0.2 O2, Al2O3, LiMn 0.6 Fe 0.4 PO4, Li 1.3 Al 0.3 Ti 1.7 The weight ratio of the four components (PO4)3 is 100:1:25:3.

[0085] The solid-state lithium battery prepared in this comparative example was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.2 Ah at a 0.33C rate and a mass energy density of 348.6 Wh / kg; the ratio of the discharge capacity at a 6C rate to the discharge capacity at 0.33C was 81.1%; the ratio of the capacity at a 3C rate constant current charge to the capacity at a constant voltage charge was 95.1%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 83.1%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0086] It is evident that, although coating the surface of ternary materials with an additional layer of Al2O3 nanoparticles does not cause fire or explosion during the 5mm needle penetration test, it will reduce the battery's energy density, high-current charge and discharge capacity, and cycle performance.

[0087] Comparative Example 9 This comparative example is basically the same as Example 1, except that: in step (1) of this comparative example, when the positive electrode sheet is made, the solid electrolyte in the positive electrode active material is Li. 1.3 Al 0.3 Ti 1.7 (PO4)3.

[0088] The solid-state lithium battery prepared in this comparative example was subjected to electrochemical performance testing under a pressure of 50 MPa. The results showed that the battery had a discharge capacity of 55.2 Ah at a 0.33C rate and a mass energy density of 238.1 Wh / kg; the ratio of the discharge capacity at a 6C rate to the 0.33C discharge capacity was 78.5%; the ratio of the capacity at a 3C rate constant current charge to (3C rate constant current charge capacity + constant voltage charge capacity) was 92.5%; after 1000 cycles of charging at a 1C rate and discharging at a 3C rate, the capacity retention rate was 79.8%; and the battery did not catch fire or explode during a 5 mm needle penetration test.

[0089] Therefore, it can be seen that conventional solid electrolyte Li is used in the preparation of positive electrode active materials. 1.3 Al 0.3 Ti 1.7 Although (PO4)3 does not catch fire or explode during a 5mm needle penetration test, it will reduce the high current charge and discharge capacity and cycle performance of the resulting battery.

[0090] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0091] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A positive electrode plate, characterized in that, It includes a positive current collector and a positive active material layer coated on the positive current collector; the positive active material layer includes a positive active material, a positive conductive agent and a positive binder; the positive active material includes a ternary material and lithium manganese iron phosphate and a functionalized solid electrolyte sequentially coated on the surface of the ternary material from the inside out.

2. The positive electrode sheet according to claim 1, characterized in that, The functionalized solid electrolyte is Li 1+3y Ti2(P 1- y M y S 4-x Se x )3, LiM’Cl6:zMt m S n any one of; wherein, M includes at least one of Ge, Si, Sn, M' includes at least one of Nb, Ta, Mt includes at least one of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn; 0 < x < 1, 0 < y < 1, 0 < z ≤ 3, m and n satisfy the stoichiometric requirements; And / or, the chemical formula of the ternary material is LiNi 1-a-b Co a Mn b O2, where 0 <a<1,0<b<1; And / or, the weight ratio of the ternary material, the lithium manganese iron phosphate and the functionalized solid electrolyte is 100:(10~50):(1~5).

3. The positive electrode sheet according to claim 1, characterized in that, The areal density of the positive electrode active material layer coated on the positive electrode current collector is 14~18 mg / cm³. 2 .

4. The positive electrode sheet according to claim 1, characterized in that, In the positive electrode active material layer, the weight ratio of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder is (90~98):(1~5):(1~5); Optionally, the positive electrode conductive agent includes at least one of conductive carbon black, conductive graphite, graphene, carbon nanotubes, and graphitized carbon fibers. Optionally, the positive electrode binder includes at least one of polyvinylidene fluoride, acrylonitrile copolymer, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

5. A method as claimed in claim 1 4. The method for preparing the positive electrode sheet according to any one of the claims, characterized in that, Includes the following steps: After stirring and mixing the positive electrode active material, positive electrode conductive agent and positive electrode binder, a positive electrode solvent is added to prepare a positive electrode slurry. The positive electrode slurry is then coated onto the positive electrode current collector, and after drying, rolling, cutting and vacuum baking, the positive electrode sheet is obtained.

6. A solid-state lithium battery, characterized in that, It includes a shell, a positive electrode, a negative electrode, and a solid electrolyte membrane; the positive electrode is as described in claim 1.

4. The positive electrode sheet according to any one of the claims or the positive electrode sheet prepared by the preparation method of claim 5.

7. The solid-state lithium battery according to claim 6, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on the negative electrode current collector; the negative electrode active material layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder; the areal density of the negative electrode active material layer coated on the negative electrode current collector is 6~9 mg / cm³. 2 .

8. The solid-state lithium battery according to claim 7, characterized in that, In the negative electrode active material layer, the weight ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is (90~98):(1~5):(1~5); Optionally, the negative electrode active material includes at least one of graphite, silicon-carbon negative electrode material, and silicon-oxygen negative electrode material; Optionally, the negative electrode conductive agent includes at least one of conductive carbon black, conductive graphite, graphene, carbon nanotubes, and graphitized carbon fibers. Optionally, the negative electrode binder includes at least one of polyvinylidene fluoride, acrylonitrile copolymer, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

9. The solid-state lithium battery according to any one of claims 6-8, characterized in that, The negative electrode sheet is prepared by a method including the following steps: mixing negative electrode active material, negative electrode conductive agent and negative electrode binder, then adding negative electrode solvent to prepare negative electrode slurry; then coating the negative electrode slurry onto the negative electrode current collector, and then drying, rolling, cutting and vacuum baking to obtain the negative electrode sheet.

10. A method for preparing a solid-state lithium battery as described in any one of claims 6-9, characterized in that, Includes the following steps: Positive and negative electrode sheets are stacked alternately, and a solid electrolyte membrane is placed between adjacent positive and negative electrode sheets to form a core. The core is then dried and placed in a housing, and then pressurized and sealed to obtain the solid-state lithium battery.

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