A negative electrode, a solid-state battery, and an electrical device.

Abstract

This application provides a negative electrode sheet, a solid-state battery, and an electrical device. The negative electrode sheet provided includes a current collector, a storage layer, and a buffer layer, which are sequentially stacked. The storage layer includes first carbon particles and first metal particles, the first metal particles being used to store active ions. The buffer layer includes second carbon particles and second metal particles, the second metal particles being used to transport active ions. Active ions combine with electrons to form active ions. The median particle size of the first carbon particles is larger than that of the second carbon particles, and the mass fraction of the first metal particles is larger than that of the second metal particles. This negative electrode sheet is less prone to lithium dendrites piercing the solid electrolyte, less prone to side reactions with the solid electrolyte, and can mitigate volume changes during charging and discharging. When applied to energy storage devices, it can combine excellent cycle performance with high energy density.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a negative electrode sheet, a solid-state battery, and an electrical device. Background Technology

[0002] The frequent fires and explosions of lithium-ion batteries in recent years have made solving the safety issues of lithium-ion batteries an urgent matter. Replacing flammable organic electrolytes with solid-state electrolytes can significantly improve battery safety. Therefore, all-solid-state batteries are considered the preferred choice for next-generation power batteries. All-solid-state batteries use lithium-ion metal as the negative electrode, achieving a balance between high energy density and high safety. However, when using lithium metal as the negative electrode, lithium atoms released from the positive electrode during charging easily form lithium dendrites on the negative electrode. During discharging, the stripping of lithium atoms creates interfacial voids, resulting in poor contact between the negative electrode and the solid-solid electrolyte, leading to uneven space charge distribution. Simultaneously, direct contact between the solid electrolyte and lithium metal can also cause side reactions, generating an interfacial reaction layer, increasing interfacial impedance, and easily leading to lithium dendrite formation during battery cycling. Lithium dendrites can cause accelerated battery failure or even short circuits, posing safety risks. Summary of the Invention

[0003] To address the aforementioned issues, this application provides a negative electrode sheet that is less prone to dendrite formation and side reactions with solid electrolytes, thus mitigating volume changes during charging and discharging. When applied to energy storage devices, it combines excellent cycle performance with high energy density.

[0004] A first aspect of this application provides a negative electrode sheet, comprising: a current collector, a storage layer, and a buffer layer, wherein the current collector, storage layer, and buffer layer are stacked sequentially; the storage layer comprises a plurality of first carbon particles and a plurality of first metal particles, wherein the first metal particles are used to store active ions; the buffer layer comprises a plurality of second carbon particles and a plurality of second metal particles, wherein the second metal particles are used to transport active ions, wherein the active ions combine with electrons to form the active ions; wherein the median particle size of the first carbon particles is larger than the median particle size of the second carbon particles, and the mass fraction of the first metal particles is larger than the mass fraction of the second metal particles.

[0005] The ratio of the mass fraction M1 of the first metal particles in the storage layer to the mass fraction M2 of the second metal particles in the buffer layer is in the range of 1.25 ≤ M1 / M2 ≤ 5.

[0006] The mass fraction M1 of the first metal particles in the storage layer ranges from 20% to 70%, and the mass fraction M2 of the second metal particles in the buffer layer ranges from 9% to 50%.

[0007] Wherein, the ratio of the mass fraction C1 of the first carbon particles to the mass fraction M1 of the first metal particles in the storage layer is in the range of 0.5 ≤ C1 / M1 ≤ 3.5; the ratio of the mass fraction C2 of the second carbon particles to the mass fraction M2 of the second metal particles in the buffer layer is in the range of 1 ≤ C2 / M2 ≤ 5.

[0008] The ratio of the specific mass of the second carbon particle to the specific mass of the first carbon particle is less than or equal to 0.6.

[0009] The median particle size of the first carbon particle ranges from 2 μm to 50 μm; the median particle size of the second carbon particle ranges from 10 nm to 500 nm.

[0010] The thickness of the storage layer ranges from 20 μm to 100 μm, and the thickness of the buffer layer ranges from 1 μm to 20 μm.

[0011] The first metal particle includes at least one of Mg, Sn, Ag, In, Zn, Al, Fe, Ga, Sb, Bi, and Au; the second metal particle includes at least one of Mg, Sn, Ag, In, Zn, Al, Fe, Ga, Sb, Bi, and Au.

[0012] The first carbon particle includes at least one of natural graphite, artificial graphite, hard carbon, soft carbon, and micron-sized porous carbon; the second carbon particle includes at least one of acetylene black, Ketjen black, and super carbon black.

[0013] A second aspect of this application provides a solid-state battery, comprising: a solid electrolyte, a positive electrode, and a negative electrode as described in the embodiments of this application. The positive electrode is stacked on the surface of the solid electrolyte, and the negative electrode is stacked on the surface of the solid electrolyte opposite to the positive electrode. A buffer layer is disposed between the solid electrolyte and the storage layer.

[0014] A third aspect of this application provides an electrical device, which includes: an electrical device body and a solid-state battery as described in the embodiments of this application, wherein the solid-state battery is used to supply power to the electrical device body.

[0015] The current collector, storage layer, and buffer layer are stacked sequentially. The buffer layer prevents direct contact between the solid electrolyte and the storage layer, thus avoiding side reactions. First carbon particles and first metal particles are disposed in the storage layer. The first carbon particles not only store active ions but also provide skeletal support, mitigating volume changes in the negative electrode during charging and discharging. When the first carbon particles are graphite and the active ion is lithium, the graphite potential after lithium intercalation is close to the lithium deposition potential, facilitating lithium deposition in the storage layer. Simultaneously, the first metal particles can undergo alloying reactions with lithium, serving as lithium nucleation sites and reducing the lithium deposition interface energy. The first carbon particles and first metal particles are uniformly dispersed, thus creating multiple uniformly dispersed nucleation sites in the storage layer, optimizing lithium ion distribution and deposition. When the active ion is lithium, the buffer layer contains second metal particles. After alloying with lithium, the second metal particles act as a medium for lithium ion transport (equivalent to the function of a solid electrolyte), assisting lithium ions in crossing the buffer layer and being transported to the storage layer. The median particle size of the first carbon particle is larger than that of the second carbon particle, which has a smaller median particle size. This results in a higher lithium deposition interface energy, and the tortuosity of the voids formed after the second carbon particles accumulate is also greater, making it less likely for lithium dendrites to grow along the buffer layer, thus preventing lithium dendrites from piercing the solid electrolyte and causing a short circuit. The mass fraction of the first metal particle is greater than that of the second metal particle. When the active ion is lithium, the lithium deposition interface energy in the storage layer is lower than that in the buffer layer, and the lithium ions preferentially deposit in the first storage layer. This negative electrode is less prone to lithium dendrites piercing the solid electrolyte, less likely to undergo side reactions with the solid electrolyte, and can mitigate the volume change of the negative electrode during charging and discharging. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of the negative electrode sheet according to an embodiment of this application.

[0018] Figure 2 The negative electrode sheet of one embodiment of this application is along Figure 1 A schematic diagram of the cross-sectional structure along the AA direction.

[0019] Figure 3 This is a schematic diagram of the structure of a solid-state battery according to an embodiment of this application.

[0020] Figure 4This application describes a solid-state battery according to an embodiment of the present application. Figure 3 Schematic diagram of the cross-sectional structure in the middle BB direction.

[0021] Figure 5 This is a schematic diagram of the structure of an electrical device according to an embodiment of this application.

[0022] Explanation of reference numerals in the attached figures:

[0023] 100 - Negative electrode, 110 - Current collector, 120 - Storage layer, 121 - First carbon particle, 122 - First metal particle, 130 - Buffer layer, 131 - Second carbon particle, 132 - Second metal particle, 200 - Solid-state battery, 210 - Solid electrolyte, 220 - Positive electrode, 300 - Electrical device, 310 - Electrical device body. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0025] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0026] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0027] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0028] The frequent fires and explosions of lithium-ion batteries in recent years have made solving the safety issues of lithium-ion batteries an urgent matter. Replacing flammable organic electrolytes with solid-state electrolytes can significantly improve battery safety. Therefore, all-solid-state batteries are considered the preferred choice for next-generation power batteries. All-solid-state batteries use lithium-ion metal as the negative electrode, achieving a balance between high energy density and high safety. However, when using lithium metal as the negative electrode, lithium atoms released from the positive electrode during charging easily form lithium dendrites on the negative electrode. During discharging, the stripping of lithium atoms creates interfacial voids, resulting in poor contact between the negative electrode and the solid-solid electrolyte, leading to uneven space charge distribution. Simultaneously, direct contact between the solid electrolyte and lithium metal can also cause side reactions, generating an interfacial reaction layer, increasing interfacial impedance, and easily leading to lithium dendrite formation during battery cycling. Lithium dendrites can cause accelerated battery failure or even short circuits, posing safety risks.

[0029] Please see Figure 1 and Figure 2 The first aspect of this application provides a negative electrode 100, which includes a current collector 110, a storage layer 120, and a buffer layer 130. The current collector 110, the storage layer 120, and the buffer layer 130 are stacked sequentially. The storage layer 120 includes a plurality of first carbon particles 121 and a plurality of first metal particles 122, the first metal particles 122 being used to store active ions. The buffer layer 130 includes a plurality of second carbon particles 131 and a plurality of second metal particles 132, the second metal particles 132 being used to transport active ions. The active ions combine with electrons to form the active ions. The median particle size of the first carbon particles 121 is larger than the median particle size of the second carbon particles 131, and the mass fraction of the first metal particles 122 is larger than the mass fraction of the second metal particles 132.

[0030] It can be understood that the current collector 110, the storage layer 120 and the buffer layer 130 are stacked in sequence, that is, the storage layer 120 is disposed on the surface of the current collector 110 and the buffer layer 130 is disposed on the surface of the storage layer 120 away from the current collector 110.

[0031] It is understood that the active ions may be, but are not limited to, lithium ions, sodium ions, etc. The lithium ions combine with electrons to form lithium atoms, and the sodium ions combine with electrons to form sodium atoms.

[0032] It is understandable that when active ions are stored in the first metal particle 122, the active ions receive electrons, form atoms, and alloy with the first metal particle 122 to form an alloy, thereby realizing the storage of active ions in the first metal particle 122.

[0033] It is understood that the plurality of first carbon particles 121 and the plurality of first metal particles 122 are uniformly dispersed in the storage layer 120, and the plurality of second carbon particles 131 and the plurality of second metal particles 132 are uniformly dispersed in the buffer layer 130.

[0034] The current collector 110, storage layer 120, and buffer layer 130 are sequentially stacked. The buffer layer 130 prevents direct contact between the solid electrolyte 210 and the storage layer 120, thus avoiding side reactions. First carbon particles 121 and first metal particles 122 are disposed in the storage layer 120. The first carbon particles 121 not only store active ions but also provide skeletal support, mitigating volume changes in the negative electrode 100 during charging and discharging. When the first carbon particles 121 are graphite and the active ion is lithium ion, the graphite potential after lithium intercalation is close to the lithium deposition potential, facilitating lithium deposition in the storage layer 120. When the active ion is lithium, the first metal particles 122 can undergo an alloying reaction with lithium, serving as lithium nucleation sites and reducing the lithium deposition interface energy. The first carbon particles 121 and first metal particles 122 are uniformly dispersed, thereby constructing multiple uniformly dispersed nucleation sites in the storage layer 120, optimizing the distribution and deposition of lithium ions. When the active ion is lithium, the buffer layer 130 contains the second metal particles 132. After alloying with lithium, the second metal particles 132 act as a medium for lithium-ion transport (equivalent to the function of the solid electrolyte 210), assisting lithium ions to cross the buffer layer 130 and be transported to the storage layer 120. The median particle size of the first carbon particles 121 is larger than that of the second carbon particles 131, which have a smaller median particle size, resulting in a higher lithium deposition interface energy. Furthermore, the tortuosity of the voids formed by the accumulation of the second carbon particles 131 is also greater, making it less likely for lithium dendrites to grow along the buffer layer 130, thus preventing lithium dendrites from piercing the solid electrolyte 210 and causing a short circuit. The mass fraction of the first metal particles 122 is greater than that of the second metal particles 132. When the active ion is lithium, the lithium deposition interface energy in the storage layer 120 is lower than that in the buffer layer 130, and the lithium ions preferentially deposit in the first storage layer 120. The negative electrode 100 is less likely to produce lithium dendrites that pierce the solid electrolyte 210, is less likely to have side reactions with the solid electrolyte 210, and can mitigate the volume change of the negative electrode 100 during the charging and discharging process.

[0035] It should be noted that, for ease of explanation, the active ion is often described as lithium ion in the embodiments.

[0036] In some embodiments, the porosity of the storage layer 120 ranges from 30% to 50%.

[0037] In the embodiments of this application, when the numerical range a to b is involved, unless otherwise specified, the numerical value can be any value between a and b, including the endpoint value a and the endpoint value b.

[0038] Specifically, the porosity of the storage layer 120 can be 30%, 35%, 40%, 45%, 50%, or any value between the above values.

[0039] When the porosity of the storage layer 120 is less than 30%, the deposition space for active ions is reduced, leading to a decrease in the energy density of the solid-state battery 200. When the porosity of the storage layer 120 is greater than 50%, the electrochemical impedance of the storage layer 120 increases, affecting the cycle performance of the solid-state battery 200. When the porosity of the storage layer 120 is between 30% and 50%, the solid-state battery 200 can achieve both high energy density and excellent cycle performance.

[0040] In some embodiments, the ratio of the mass fraction M1 of the first metal particles 122 in the storage layer 120 to the mass fraction M2 of the second metal particles 132 in the buffer layer 130 is in the range of 1.25 ≤ M1 / M2 ≤ 5.

[0041] It is understood that the mass fraction M1 of the first metal particles 122 in the storage layer 120 refers to the percentage of the mass of the first metal particles 122 in the storage layer 120 to the total mass of the storage layer 120; and the mass fraction M2 of the second metal particles 132 in the buffer layer 130 refers to the percentage of the mass of the first metal particles 122 in the buffer layer 130 to the total mass of the buffer layer 130.

[0042] Specifically, the ratio of the mass fraction M1 of the first metal particles 122 in the storage layer 120 to the mass fraction M2 of the second metal particles 132 in the buffer layer 130 can be 1.25, 2, 3, 4, 5, or any value between the above values.

[0043] When the ratio of the mass fraction M1 of the first metal particles 122 in the storage layer 120 to the mass fraction M2 of the second metal particles 132 in the buffer layer 130 is less than 1.25, and the active ion is lithium ion, the lithium ion will also deposit in the buffer layer 130. Lithium dendrites easily grow along the buffer layer 130 and can easily pierce the solid electrolyte 210, causing a short circuit. When the ratio of the mass fraction M1 of the first metal particles 122 in the storage layer 120 to the mass fraction M2 of the second metal particles 132 in the buffer layer 130 is greater than 5, the second metal particles 132 cannot help the active ions cross the buffer layer 130, causing the active ions to deposit in the buffer layer 130. When the ratio of the mass fraction M1 of the first metal particles 122 in the storage layer 120 to the mass fraction M2 of the second metal particles 132 in the buffer layer 130 is between 1.25 and 5, the active ions are not easily deposited in the buffer layer 130, and can also help the active ions cross the buffer layer 130, so that lithium ions are deposited in the storage layer 120.

[0044] In some embodiments, the mass fraction M1 of the first metal particles 122 in the storage layer 120 is in the range of 20% ≤ M1 ≤ 70%. Specifically, the mass fraction of the first metal particles 122 in the storage layer 120 can be 20%, 30%, 40%, 50%, 60%, 70%, or any value between the above values.

[0045] When the mass fraction of the first metal particles 122 in the storage layer 120 is less than 20%, the first metal particles 122 cannot construct multiple uniformly dispersed nucleation sites in the storage layer 120, and cannot optimize the distribution and deposition of active ions. When the mass fraction of the first metal particles 122 in the storage layer 120 is greater than 70%, the storage layer 120 cannot mitigate the volume change of the negative electrode 100 during charging and discharging. When the mass fraction of the first metal particles 122 in the storage layer 120 is between 20% and 70%, the first metal particles 122 can construct multiple uniformly dispersed nucleation sites in the storage layer 120, optimizing the distribution and deposition of active ions, and the storage layer 120 can also mitigate the volume change of the negative electrode 100 during charging and discharging.

[0046] In some embodiments, the mass fraction M2 of the second metal particles 132 in the buffer layer 130 is in the range of 9% ≤ M2 ≤ 50%. Specifically, the mass fraction of the second metal particles 132 in the buffer layer 130 can be 9%, 10%, 20%, 30%, 40%, 50%, or any value between the above values.

[0047] When the mass fraction of the second metal particles 132 in the buffer layer 130 is less than 9%, the second metal particles 132 cannot help active ions cross the buffer layer 130, preventing active ions from depositing in the buffer layer 130. When the mass fraction of the second metal particles 132 in the buffer layer 130 is greater than 50%, and the active ion is lithium ion, the lithium ion will also deposit in the buffer layer 130. Lithium dendrites easily grow along the buffer layer 130 and can easily pierce the solid electrolyte 210, causing a short circuit. When the mass fraction of the second metal particles 132 in the buffer layer 130 is between 9% and 50%, and the active ion is lithium ion, the second metal particles 132 can both help lithium ions cross the buffer layer 130, allowing lithium ions to deposit in the storage layer 120, and can also prevent lithium ions from depositing in the buffer layer 130.

[0048] In some embodiments, the ratio of the mass fraction C1 of the first carbon particle 121 to the mass fraction M1 of the first metal particle 122 in the storage layer 120 is in the range of 0.5 ≤ C1 / M1 ≤ 3.5.

[0049] It is understood that the mass fraction C1 of the first carbon particles 121 in the storage layer 120 refers to the percentage of the mass of the first carbon particles 121 in the storage layer 120 to the total mass of the storage layer 120.

[0050] Specifically, the ratio of the mass fraction C1 of the first carbon particle 121 to the mass fraction M1 of the first metal particle 122 can be 0.5, 1, 2, 3, 3.5, or any value between the above.

[0051] When the ratio of the mass fraction C1 of the first carbon particles 121 to the mass fraction M1 of the first metal particles 122 is less than 0.5, the number of first carbon particles 121 is insufficient, which cannot alleviate the volume change of the negative electrode 100 during charging and discharging. When the ratio of the mass fraction C1 of the first carbon particles 121 to the mass fraction M1 of the first metal particles 122 is greater than 3.5, the first metal particles 122 cannot construct multiple uniformly dispersed nucleation sites in the storage layer 120, and cannot optimize the distribution and deposition of active ions, resulting in a lower cycle capacity retention rate of the solid-state battery 200. When the ratio of the mass fraction C1 of the first carbon particles 121 to the mass fraction M1 of the first metal particles 122 is between 0.5 and 3.5, the first metal particles 122 can construct multiple uniformly dispersed nucleation sites in the storage layer 120, optimizing the distribution and deposition of active ions, and the storage layer 120 can alleviate the volume change of the negative electrode 100 during charging and discharging.

[0052] In some embodiments, the ratio of the mass fraction C2 of the second carbon particle 131 to the mass fraction M2 of the second metal particle 132 in the buffer layer is in the range of 1≤C2 / M2≤5.

[0053] It is understood that the mass fraction C2 of the second carbon particles 131 in the buffer layer 130 refers to the percentage of the mass of the second carbon particles 131 in the buffer layer 130 to the total mass of the buffer layer 130.

[0054] Specifically, the ratio of the mass fraction C2 of the second carbon particle 131 to the mass fraction M2 of the second metal particle 132 can be 1, 2, 3, 4, 5, or any value between the above.

[0055] When the ratio of the mass fraction C2 of the second carbon particles 131 to the mass fraction M2 of the second metal particles 132 is less than 1, and the active ion is lithium ion, the lithium ion will also deposit in the buffer layer 130. Lithium dendrites easily grow along the buffer layer 130 and can easily pierce the solid electrolyte 210, causing a short circuit. When the ratio of the mass fraction C2 of the second carbon particles 131 to the mass fraction M2 of the second metal particles 132 is greater than 5, the second metal particles 132 cannot help the active ion cross the buffer layer 130, causing the active ion to deposit on the surface of the buffer layer 130, resulting in the formation of lithium dendrites, which deteriorates the cycle performance and may even cause a short circuit in the solid-state battery 200. When the ratio of the mass fraction C2 of the second carbon particles 131 to the mass fraction M2 of the second metal particles 132 is between 1 and 5, and the active ion is lithium ion, the second metal particles 132 can both help lithium ion cross the buffer layer 130, causing lithium ion to deposit in the buffer layer 130, and can also prevent lithium ion from depositing in the buffer layer 130.

[0056] In some embodiments, the ratio of the specific mass of the second carbon particle 131 to the specific mass of the first carbon particle 121 is less than or equal to 0.6.

[0057] When the ratio of the specific capacity of the second carbon particle 131 to the specific capacity of the first carbon particle 121 is less than or equal to 0.6, and the active ion is lithium ion, it is more difficult for lithium ions to intercalate in the second carbon particle 131, and lithium dendrites will not grow along the buffer layer 130, thereby improving the safety of the solid-state battery 200.

[0058] In some embodiments, the specific capacity of the first carbon particle 121 is greater than or equal to 180 mAh / g, and the specific capacity of the second carbon particle 131 is less than or equal to 100 Ah / g.

[0059] When the specific capacity of the first carbon particle 121 is greater than or equal to 180 mAh / g and the specific capacity of the second carbon particle 131 is less than or equal to 100 Ah / g, and the active ion is lithium ion, the lithium ion is more easily intercalated in the first carbon particle 121, which can improve the energy density of the solid-state battery 200 using the negative electrode 100. The lithium ion is less easily intercalated in the second carbon particle 131, and lithium dendrites will not grow along the buffer layer 130, improving the safety of the solid-state battery 200.

[0060] In some embodiments, the specific capacity of the first carbon particle 121 is from 180 mAh / g to 372 mAh / g. Specifically, the specific capacity of the first carbon particle 121 can be, but is not limited to, 180 mAh / g, 200 mAh / g, 220 mAh / g, 240 mAh / g, 260 mAh / g, 280 mAh / g, 300 mAh / g, 320 mAh / g, 340 mAh / g, 360 mAh / g, 372 mAh / g, and any value between the above values.

[0061] When the specific capacity of the first carbon particle 121 is less than 180 mAh / g, the specific capacity of the first carbon particle 121 is too small, resulting in a decrease in the energy density of the solid-state battery 200. The specific capacity of the first carbon particle 121 is difficult to exceed 372 mAh / g; if the specific capacity of the first carbon particle 121 is too large, it is difficult to achieve with existing materials. When the specific capacity of the first carbon particle 121 is between 180 mAh / g and 372 mAh / g, the energy density of the solid-state battery 200 can be maximized with existing materials.

[0062] Optionally, the specific capacity of the second carbon particle 131 can also be 0 mAh / g. Understandably, the specific capacity of the second carbon particle 131 ranges from 0 to 100 Ah / g. Specifically, the specific capacity of the second carbon particle 131 can be, but is not limited to, 0 mAh / g, 10 mAh / g, 20 mAh / g, 30 mAh / g, 40 mAh / g, 50 mAh / g, 60 mAh / g, 70 mAh / g, 80 mAh / g, 90 mAh / g, 100 mAh / g, and any value between the above.

[0063] When the specific capacity of the second carbon particle 131 is 0 mAh / g, and the active ion is lithium ion, the lithium ion will not be intercalated in the second carbon particle 131, and lithium dendrites will not grow along the buffer layer 130, thereby improving the safety of the solid-state battery 200.

[0064] In some embodiments, the first carbon particle 121 first-round lithium intercalation yields C6Li x In the figure, x values ​​range from 0.5 to 1; the first carbon particle 121 is used to insert lithium into C6Li. yIn the given information, the y-value is less than 0.5.

[0065] When the first carbon particle 121 undergoes its first lithium intercalation, C6Li is obtained. x In the figure, x values ​​range from 0.5 to 1; the first carbon particle 121 is used to insert lithium into C6Li. y When the y-value is less than 0.5, lithium ions are more easily intercalated in the first carbon particle 121, which can improve the energy density of the solid-state battery 200 using the negative electrode 100. Lithium ions are less easily intercalated in the second carbon particle 131, and lithium dendrites will not grow along the buffer layer 130, thus improving the safety of the solid-state battery 200.

[0066] In some embodiments, the ratio of the median particle size of the second carbon particle 131 to the median particle size of the first carbon particle 121 ranges from 0.0005 to 0.03. Specifically, the ratio of the median particle size of the second carbon particle 131 to the median particle size of the first carbon particle 121 can be 0.0005, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, and any value between the above values.

[0067] When the ratio of the median particle size of the second carbon particle 131 to the median particle size of the first carbon particle 121 is less than 0.0005, the porosity of the buffer layer 130 is low, making it difficult for lithium ions to pass through the buffer layer 130 when the active ion is lithium ions. When the ratio of the median particle size of the second carbon particle 131 to the median particle size of the first carbon particle 121 is greater than 0.03, it is not easy to control the thickness of the interface buffer layer 130, nor can the tortuosity of the buffer layer 130 be greatly improved. The effect on inhibiting the penetration growth of lithium dendrites is not obvious, and the specific surface area of ​​the second carbon particle 131 is small, which cannot increase the contact area between the solid electrolyte 210 and the storage layer 120. When the ratio of the median particle size of the second carbon particle 131 to the median particle size of the first carbon particle 121 is between 0.0005 and 0.03, the lithium ions can easily pass through the buffer layer 130, making it easier to control the thickness of the interface buffer layer 130 and significantly improving the tortuosity of the buffer layer 130, thus inhibiting the penetration growth of lithium dendrites. The second carbon particle 131 has a larger specific surface area, which can increase the contact area between the solid electrolyte 210 and the storage layer 120.

[0068] In some embodiments, the median particle size of the first carbon particle 121 ranges from 2 μm to 20 μm.

[0069] Specifically, the median particle size of the first carbon particle 121 can be 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, or any value between the above values.

[0070] It is understood that the median particle size refers to the particle size corresponding to a cumulative particle size distribution percentage of 50% for the sample.

[0071] When the median particle size of the first carbon particles 121 is less than 2 μm, the porosity of the storage layer 120 is low, resulting in reduced deposition space for active ions and affecting the energy density of the solid-state battery 200. When the median particle size of the first carbon particles 121 is greater than 20 μm, it affects the kinetic performance of the active ions and makes it difficult to control the thickness of the lithium storage layer, thus affecting the energy density and cycle performance of the solid-state battery 200. When the median particle size of the first carbon particles 121 is between 2 μm and 20 μm, the porosity of the storage layer 120 is high, which can balance the high energy density and good cycle performance of the solid-state battery 200.

[0072] Furthermore, the median particle size of the first carbon particle 121 ranges from 3 μm to 10 μm.

[0073] When the median particle size of the first carbon particle 121 is between 3 μm and 10 μm, it can further balance the high energy density and good cycle performance of the solid-state battery 200.

[0074] In some embodiments, the median particle size of the second carbon particle 131 ranges from 10 nm to 500 nm.

[0075] Specifically, the median particle size of the second carbon particle 131 can be 10nm, 100nm, 200nm, 300nm, 400nm, 500nm, or any value between the above values.

[0076] When the median particle size of the second carbon particles 131 is less than 10 nm, the porosity of the buffer layer 130 is low, making it difficult for lithium ions to pass through the buffer layer 130 when the active ion is lithium ion. When the median particle size of the second carbon particles 131 is greater than 500 nm, it is difficult to control the thickness of the interface buffer layer 130, and the tortuosity of the buffer layer 130 cannot be greatly improved. The effect on suppressing the penetration growth of lithium dendrites is not significant, and the specific surface area of ​​the second carbon particles 131 is small, which cannot increase the contact area between the solid electrolyte 210 and the storage layer 120. When the median particle size of the second carbon particles 131 is between 10 nm and 500 nm, lithium ions can easily pass through the buffer layer 130, the thickness of the interface buffer layer 130 is easy to control, and the tortuosity of the buffer layer 130 can be significantly improved, suppressing the penetration growth of lithium dendrites. The specific surface area of ​​the second carbon particles 131 is large, which can increase the contact area between the solid electrolyte 210 and the storage layer 120.

[0077] Furthermore, the median particle size of the second carbon particle 131 ranges from 10 nm to 100 nm. Specifically, the median particle size of the second carbon particle 131 can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value between the above values.

[0078] When the median particle size of the second carbon particle 131 is between 10 nm and 100 nm, it is easier to control the thickness of the interface buffer layer 130 and can also greatly improve the tortuosity of the buffer layer 130. When the active ion is lithium ion, it inhibits the penetration growth of lithium dendrites. The second carbon particle 131 has a large specific surface area, which can significantly improve the contact area between the solid electrolyte 210 and the storage layer 120.

[0079] In some embodiments, the first carbon particle 121 includes at least one of natural graphite, artificial graphite, hard carbon, soft carbon, and micron-sized porous carbon.

[0080] When the first carbon particle 121 includes at least one of natural graphite, artificial graphite, hard carbon, soft carbon, and micron-porous carbon, the first carbon particle 121 can not only store active ions, but also play a supporting role in the skeleton, thus mitigating the volume change of the negative electrode 100 during the charging and discharging process.

[0081] In some embodiments, the second carbon particle 131 includes at least one of acetylene black, Ketjen black, and super carbon black (i.e., Super P carbon black).

[0082] It is understood that the super carbon black is Super P carbon black.

[0083] When the second carbon particle 131 includes at least one of acetylene black, Ketjen black, and super carbon black (i.e., Super P carbon black), lithium will not be intercalated in the second carbon particle 131, and the tortuosity of the voids formed after accumulation is also large. When the active ion is lithium ion, lithium dendrites are not easy to grow along this layer, preventing lithium dendrites from piercing the solid electrolyte 210 and causing a short circuit.

[0084] In some embodiments, the thickness of the storage layer 120 is greater than the thickness of the buffer layer 130.

[0085] When the thickness of the storage layer 120 is greater than the thickness of the buffer layer 130, and the active ion is lithium ion, the lithium ion can easily pass through the buffer layer 130 into the storage layer 120, and the lithium intercalation capacity of the negative electrode 100 can also be increased, and the solid-state battery 200 has a higher energy density.

[0086] In some embodiments, the thickness of the storage layer 120 ranges from 20 μm to 100 μm.

[0087] Specifically, the thickness of the storage layer 120 can be 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, or any value between the above values.

[0088] When the thickness of the storage layer 120 is less than 20 μm, the negative electrode 100 applied to the solid-state battery 200 significantly reduces the energy density of the solid-state battery 200. When the thickness of the storage layer 120 is greater than 100 μm, the electrochemical impedance of the solid-state battery 200 increases when the negative electrode 100 is applied to the solid-state battery 200, affecting the cycle performance of the solid-state battery 200. When the thickness of the storage layer 120 is between 20 μm and 100 μm, the solid-state battery 200 can achieve both high energy density and good cycle performance.

[0089] Furthermore, the thickness of the storage layer 120 ranges from 30 μm to 50 μm. Specifically, the thickness of the storage layer 120 can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any value between these values.

[0090] When the thickness of the storage layer 120 is between 30 μm and 50 μm, the solid-state battery 200 can further balance high energy density and good cycle performance.

[0091] In some embodiments, the thickness of the buffer layer 130 ranges from 1 μm to 20 μm. Specifically, the thickness of the buffer layer 130 can be 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, or any value between these values.

[0092] When the thickness of the buffer layer 130 is less than 1 μm, it is prone to cracking during the cycling process of the solid-state battery 200, affecting its protective effect on the storage layer 120. When the thickness of the buffer layer 130 is greater than 20 μm, it prolongs the transport path of active ions in the buffer layer 130, increasing the internal resistance of the solid-state battery 200. When the thickness of the buffer layer 130 is between 1 μm and 20 μm, it is less likely to crack during the cycling process of the solid-state battery 200, and the transport path of active ions in the buffer layer 130 is not significantly prolonged.

[0093] Furthermore, the thickness of the buffer layer 130 ranges from 5 μm to 15 μm.

[0094] When the thickness of the buffer layer 130 is between 5 μm and 15 μm, the buffer layer 130 is less likely to crack during the cycling of the solid-state battery 200, and the transport path of active ions in the buffer layer 130 will not be significantly prolonged.

[0095] In some embodiments, the first metal particle 122 includes at least one of Mg, Sn, Ag, In, Zn, Al, Fe, Ga, Sb, Bi, and Au.

[0096] When the first metal particle 122 includes at least one of Mg, Sn, Ag, In, Zn, Al, Fe, Ga, Sb, Bi, and Au, and the active ion is a lithium ion, the first metal particle 122 can become a lithium nucleation site, reducing the lithium deposition interface energy.

[0097] In some embodiments, the second metal particle 132 includes at least one of Mg, Sn, Ag, In, Zn, Al, Fe, Ga, Sb, Bi, and Au.

[0098] When the second metal particle 132 includes at least one of Mg, Sn, Ag, In, Zn, Al, Fe, Ga, Sb, Bi, and Au, and the active ion is a lithium ion, the second metal particle 132 can be alloyed with lithium to assist lithium ions in crossing the buffer layer 130, so that lithium ions are deposited into the storage layer 120.

[0099] In some embodiments, the median particle size of the first metal particle 122 is between 1 nm and 500 nm. Specifically, the median particle size of the first metal particle 122 can be 1 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or any value between the above values.

[0100] When the median particle size of the first metal particles 122 is less than 1 nm, the manufacturing cost of the first metal particles 122 is too high. When the median particle size of the first metal particles 122 is greater than 500 nm, the kinetics of the reaction between the first metal particles 122 and the active ions are slow, and the first metal particles 122 are also difficult to distribute uniformly in the storage layer 120. When the median particle size of the first metal particles 122 is between 1 nm and 500 nm, the kinetics of the reaction between the first metal particles 122 and the active ions are fast, and the first metal particles 122 can also be more easily and uniformly distributed in the storage layer 120.

[0101] Furthermore, the median particle size of the first metal particle 122 is between 10 nm and 100 nm. Specifically, the median particle size of the first metal particle 122 can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value between the above values.

[0102] When the median particle size of the first metal particle 122 is between 10 nm and 500 nm, the kinetics of the reaction between the first metal particle 122 and the active ions are faster, and the first metal particle 122 can also be more easily and uniformly distributed in the storage layer 120.

[0103] In some embodiments, the median particle size of the second metal particle 132 is between 1 nm and 500 nm. Specifically, the median particle size of the second metal particle 132 can be 1 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or any value between the above values.

[0104] When the median particle size of the second metal particle 132 is less than 1 nm, the manufacturing cost of the second metal particle 132 is too high. When the median particle size of the second metal particle 132 is greater than 500 nm, the second metal particle 132 cannot quickly conduct active ions to the storage layer 120, and the second metal particle 132 is also difficult to distribute uniformly in the buffer layer 130. When the active ion is lithium ion, it leads to the formation of lithium dendrites. When the median particle size of the second metal particle 132 is between 1 nm and 500 nm, the second metal particle 132 can quickly conduct active ions to the storage layer 120, and the second metal particle 132 is also easy to distribute uniformly in the buffer layer 130.

[0105] Furthermore, the median particle size of the second metal particle 132 is between 10 nm and 100 nm. Specifically, the median particle size of the second metal particle 132 can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value between the above values.

[0106] When the median particle size of the second metal particle 132 is between 10 nm and 100 nm, the second metal particle 132 can quickly conduct active ions to the storage layer 120, and the second metal particle 132 is also more easily and evenly distributed in the buffer layer 130.

[0107] In some embodiments, the storage layer 120 further includes a first adhesive, which is at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF HFP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyamide (PI), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), sodium alginate (Alg), and polyethylene oxide (PEO).

[0108] When the storage layer 120 further includes a first binder, the first carbon particles 121 and the first metal particles 122 are not easily detached.

[0109] In some embodiments, the mass fraction of the first adhesive in the storage layer 120 ranges from 0.1% to 10%.

[0110] When the mass fraction of the first binder is less than 0.1%, the first carbon particles 121 and the first metal particles 122 are relatively easy to detach. When the mass fraction of the first binder is greater than 10%, the energy density of the solid-state battery 200 is low when the storage layer 120 is applied. When the mass fraction of the first binder is between 0.1% and 10%, the first carbon particles 121 and the first metal particles 122 are not easily detached, and the energy density of the solid-state battery 200 does not decrease significantly when the storage layer 120 is applied.

[0111] In some embodiments, the buffer layer 130 further includes a second adhesive, which is at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF HFP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyamide (PI), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), sodium alginate (Alg), and polyethylene oxide (PEO).

[0112] When the buffer layer 130 further includes a second adhesive, the second carbon particles 131 and the second metal particles 132 are less likely to fall off.

[0113] In some embodiments, the mass fraction of the second adhesive in the buffer layer 130 ranges from 0.1% to 10%.

[0114] When the mass fraction of the second binder is less than 0.1%, the second carbon particles 131 and the second metal particles 132 are relatively easy to detach. When the mass fraction of the second binder is greater than 10%, the energy density of the solid-state battery 200 is low when the buffer layer 130 is applied. When the mass fraction of the second binder is between 0.1% and 10%, the second carbon particles 131 and the second metal particles 132 are not easily detached, and the energy density of the solid-state battery 200 does not decrease significantly when the buffer layer 130 is applied.

[0115] Please see Figure 3 and Figure 4 This application provides a solid-state battery 200, which includes: a solid electrolyte 210, a positive electrode 220, and a negative electrode 100 as described in this application embodiment. The positive electrode 220 is stacked on the surface of the solid electrolyte 210, and the negative electrode 100 is stacked on the surface of the solid electrolyte 210 opposite to the positive electrode 220. The buffer layer 130 is disposed between the solid electrolyte 210 and the storage layer 120.

[0116] In some embodiments, the solid electrolyte 210 may be at least one of the following: ceramic oxide with garnet structure, ceramic oxide with perovskite structure, NaSICON type ceramic electrolyte, LiPON solid electrolyte 210, and sulfide type solid electrolyte 210.

[0117] The present application is further illustrated below with reference to embodiments. It should be understood that the embodiments provided in this application are merely for the purpose of understanding the present application and should not be regarded as specific limitations on the present application.

[0118] For ease of understanding, the following embodiments are provided in this application. Those skilled in the art should understand that unless specific conditions are specified in the embodiments, conventional conditions should be followed.

[0119] Examples 1 to 17

[0120] (1) Preparation of composite storage layer 120:

[0121] The first carbon particles 121 and the first metal particles 122 were ball-milled in a certain ratio and mixed with 5 wt% polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) at a speed of 1200 r / min for 6 hours. The mixture was then coated onto a stainless steel substrate using a blade coating method, vacuum dried at 80°C for 2 hours, and then rolled to obtain a composite layer of storage layer 120 and current collector 110. The particle size and ratio of the first carbon particles 121 and the first metal particles 122 in Examples 1 to 17 are shown in Tables 1 and 2.

[0122] (2) Preparation of interface buffer layer 130:

[0123] The second carbon particles 131 and the second metal particles 132 were mixed in a certain proportion, and then 5 wt% polyvinylidene fluoride (PVDF) was added to an N-methylpyrrolidone (NMP) solution. The mixture was stirred at 1200 r / min for 6 hours. The mixture was then coated onto the storage layer 120 using a blade coating method and vacuum dried at 80°C for 2 hours to obtain the negative electrode 100. The particle size and ratio of the second carbon particles 131 and the second metal particles 132 in Examples 1 to 17 are shown in Tables 1 and 2.

[0124] (3) Preparation of positive electrode powder:

[0125] NCM622 cathode particles, LiPSCl, and acetylene black were mixed in a mass ratio of 55:42:3, with approximately 10 mg of NCM622 active material. The mixture was then ground until homogeneous to obtain cathode powder.

[0126] (4) Solid-state battery 200 assembly:

[0127] The composite layer of storage layer 120 and current collector 110 is cut into a circular piece with a diameter of 10 mm, placed into a solid-state battery 200 mold with a 10 mm aperture, 100 mg of LiPSCl electrolyte powder is added, and a pressure of 1 ton is applied for pre-compression; then, positive electrode powder is added, and a pressure of 2.5 tons is applied to finally obtain the solid-state battery 200 of Examples 1 to 17.

[0128] Example 18

[0129] (1) Preparation of composite storage layer 120:

[0130] The first carbon particles 121 and the first metal particles 122 were ball-milled in a certain ratio and mixed with 5 wt% sodium alginate in N-methylpyrrolidone (NMP) at a speed of 1200 r / min for 6 hours. The mixture was then coated onto a stainless steel substrate using a blade coating method, vacuum dried at 80°C for 2 hours, and then rolled to obtain a composite layer of storage layer 120 and current collector 110. The particle size and ratio of the first carbon particles 121 and the first metal particles 122 in Example 18 are shown in Tables 1 and 2.

[0131] (2) Preparation of interface buffer layer 130:

[0132] The second carbon particles 131 and the second metal particles 132 were mixed in a certain proportion, and then 5 wt% sodium alginate was added to an N-methylpyrrolidone (NMP) solution. The mixture was stirred at 1200 r / min for 6 hours. The mixture was then coated onto the storage layer 120 using a blade coating method and dried under vacuum at 80°C for 2 hours to obtain the negative electrode 100. The particle size and ratio of the second carbon particles 131 and the second metal particles 132 in Example 18 are shown in Tables 1 and 2.

[0133] (3) Preparation of positive electrode powder: The preparation method is the same as that of positive electrode powder in Example 1.

[0134] (4) Solid-state battery 200 assembly: The solid-state battery 200 assembly method is the same as that in Example 1.

[0135] Comparative Example 1

[0136] (1) Preparation of composite storage layer 120:

[0137] The first carbon particles 121 and the first metal particles 122 were ball-milled in a certain proportion and mixed with 5 wt% polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) at a speed of 1200 r / min for 6 hours. The mixture was then coated onto a stainless steel substrate using a blade coating method, vacuum dried at 80°C for 2 hours, and then rolled to obtain a composite layer of storage layer 120 and current collector 110. The particle size and ratio of the first carbon particles 121 and the first metal particles 122 in Comparative Example 1 are shown in Table 1.

[0138] (2) Preparation of positive electrode powder:

[0139] NCM622 cathode particles, LiPSCl, and acetylene black were mixed in a mass ratio of 55:42:3, with approximately 10 mg of NCM622 active material. The mixture was then ground until homogeneous to obtain cathode powder.

[0140] (3) Solid-state battery 200 assembly:

[0141] The composite layer of storage layer 120 and current collector 110 is cut into a circular piece with a diameter of 10 mm, placed into a solid-state battery 200 mold with a 10 mm aperture, 100 mg of LiPSCl electrolyte powder is added, and a pressure of 1 ton is applied for pre-compression; then, positive electrode powder is added, and a pressure of 2.5 tons is applied to finally obtain solid-state battery 200.

[0142] Comparative Example 2

[0143] (1) Preparation of composite storage layer 120:

[0144] The first carbon particles 121 and the first metal particles 122 were ball-milled in a certain proportion and mixed with 5 wt% polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) at a speed of 1200 r / min for 6 hours. The mixture was then coated onto a stainless steel substrate using a blade coating method, vacuum dried at 80°C for 2 hours, and then rolled to obtain a composite layer of storage layer 120 and current collector 110. The particle size and proportion of the first carbon particles 121 and the first metal particles 122 in Comparative Example 2 are shown in Tables 1 and 2.

[0145] (2) Preparation of interface buffer layer 130:

[0146] The second carbon particles 131 and the second metal particles 132 were mixed in a certain proportion, and then 5 wt% polyvinylidene fluoride (PVDF) was added to an N-methylpyrrolidone (NMP) solution. The mixture was stirred at 1200 r / min for 6 hours. The mixture was then coated onto the storage layer 120 using a blade coating method and dried under vacuum at 80°C for 2 hours to obtain the negative electrode 100. The particle size and ratio of the second carbon particles 131 and the second metal particles 132 in Comparative Example 2 are shown in Tables 1 and 2.

[0147] (3) Preparation of positive electrode powder:

[0148] NCM622 cathode particles, LiPSCl, and acetylene black were mixed in a mass ratio of 55:42:3, with approximately 10 mg of NCM622 active material. The mixture was then ground until homogeneous to obtain cathode powder.

[0149] (4) Solid-state battery 200 assembly:

[0150] The composite layer of storage layer 120 and current collector 110 is cut into a circular piece with a diameter of 10 mm, placed into a solid-state battery 200 mold with a 10 mm aperture, 100 mg of LiPSCl electrolyte powder is added, and a pressure of 1 ton is applied for pre-compression; then, positive electrode powder is added, and a pressure of 2.5 tons is applied to finally obtain the solid-state battery 200 of Comparative Example 2.

[0151] Solid-state battery 200 cycle performance test

[0152] The solid-state battery 200 obtained in the above embodiments was subjected to charge-discharge cycle testing on a charge-discharge instrument. The test temperature was 45°C, the cycle rate was 1 / 3C (i.e., both the charge and discharge rates were 1 / 3C), and the charging voltage ranged from 2.8V to 4.3V. The capacity retention rate after cycling was calculated. The formula for calculating the capacity retention rate after cycling is: Capacity retention rate after the nth cycle = (Discharge capacity after the nth cycle / Maximum discharge capacity of the cycle) * 100%.

[0153] It is understood that, in this application, the term "cycle" refers to the number of times the solid-state battery 200 is charged and discharged at a preset rate. One complete charge-discharge cycle of the solid-state battery 200 is called one cycle. The capacity retention rate after 50 cycles refers to the capacity retention rate of the solid-state battery 200 after 50 charge-discharge cycles at a 1 / 3C charging rate and a 1 / 3C discharging rate.

[0154] The performance test data of the solid-state battery 200 are shown in Table 2:

[0155] Table 1:

[0156]

[0157]

[0158] Table 2:

[0159]

[0160]

[0161] As shown in Tables 1 and 2, the data from Example 1 and Comparative Example 1 show that, in Comparative Example 1, the negative electrode 100 lacks a buffer layer 130, and after 50 cycles, the capacity retention of the solid-state battery 200 has dropped to 80%. This is because Comparative Example 1 lacks a buffer layer 130 to suppress interfacial side reactions and lithium dendrite growth, resulting in a significant decrease in the capacity retention of the solid-state battery 200.

[0162] As can be seen from the data of Example 1 and Comparative Example 2, the solid-state battery 200 in Comparative Example 2 has a short circuit after 50 cycles. This is because the mass fraction of the first metal particle 122 is less than the mass fraction of the second metal particle 132. The lithium ions preferentially deposit in the buffer layer 130, which makes it easier to generate lithium dendrites, thereby piercing the solid electrolyte 210 and causing a short circuit.

[0163] Data from Examples 1, 5, and 6 show that as the median particle size of the first carbon particle 121 increases, the kinetic performance of the lithium ions deteriorates, affecting the cycle performance of the solid-state battery 200.

[0164] As can be seen from the data of Examples 1, 7 and 8, as the ratio of the mass fraction of the first carbon particle 121 to the mass fraction of the first metal particle 122 increases, the first metal particle 122 cannot construct multiple uniformly dispersed nucleation sites in the storage layer 120, and cannot optimize the distribution and deposition of lithium ions, resulting in a lower cycle capacity retention rate of the solid-state battery 200.

[0165] As can be seen from the data of Examples 1, 9 and 10, as the ratio of the mass fraction of the second carbon particle 131 to the mass fraction of the second metal particle 132 increases, the second metal particle 132 cannot help lithium ions cross the buffer layer 130, causing lithium ions to easily deposit in the buffer layer 130, resulting in the formation of lithium dendrites and a decrease in cycle capacity retention.

[0166] Data from Examples 1, 11 to 13 show that as the thickness of the buffer layer 130 increases, the growth of lithium dendrites is suppressed, and the cycle capacity retention rate increases. When the thickness of the buffer layer 130 increases to a certain value, if the thickness of the buffer layer 130 is further increased, the lithium ions cannot cross the buffer layer 130, causing lithium ions to easily deposit in the buffer layer 130, resulting in the generation of lithium dendrites and a decrease in the cycle capacity retention rate.

[0167] As can be seen from the data of Examples 1 and 16, as the median particle size of the second carbon particles 131 increases, it is not easy to control the thickness of the interface buffer layer 130, nor can the tortuosity of the buffer layer 130 be greatly improved, and the effect on suppressing the penetration growth of lithium dendrites is not obvious.

[0168] As can be seen from the data of Examples 1 and 17, when the median particle size of the second metal particle 132 increases, the second metal particle 132 cannot quickly conduct lithium ions to the storage layer 120, and the second metal particle 132 is also difficult to distribute evenly in the buffer layer 130, resulting in the formation of lithium dendrites in the negative electrode 100, which reduces the cycle capacity retention rate.

[0169] Please see Figure 5 This application provides an electrical device 300, which includes an electrical device body 310 and a solid-state battery 200 as described in this application embodiment. The solid-state battery 200 is used to supply power to the electrical device body 310. It is understood that, for ease of illustration, the solid-state battery 200 is placed outside the electrical device body 310. In normal use, the solid-state battery 200 is inside the electrical device body 310.

[0170] The electrical device 300 in this application embodiment can be, but is not limited to, mobile phones, tablets, laptops, desktop computers, smart bracelets, smartwatches, e-readers, game consoles, toys, and other electronic devices; in addition, the electrical device 300 can also be automobiles, home appliances, etc.

[0171] It is understood that the electrical device 300 described in this embodiment is merely one form of the electrical device 300 used by the solid-state battery 200, and should not be construed as a limitation on the electrical device 300 provided in this application, nor should it be construed as a limitation on the solid-state battery 200 provided in various embodiments of this application.

[0172] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A negative electrode sheet, characterized in that, The negative electrode includes a current collector, a storage layer, and a buffer layer, which are stacked sequentially. The storage layer includes multiple first carbon particles and multiple first metal particles, where the first metal particles are used to store active ions. The buffer layer includes multiple second carbon particles and multiple second metal particles, where the second metal particles are used to transport active ions. The active ions combine with electrons to form atoms. The median particle size of the first carbon particles is larger than that of the second carbon particles, and the mass fraction of the first metal particles is larger than that of the second metal particles. The ratio of the mass fraction C2 of the second carbon particles to the mass fraction M2 of the second metal particles in the buffer layer is in the range of 1 ≤ C2 / M2 ≤ 5.

2. The negative electrode sheet according to claim 1, characterized in that, The ratio of the mass fraction M1 of the first metal particles in the storage layer to the mass fraction M2 of the second metal particles in the buffer layer is in the range of 1.25 ≤ M1 / M2 ≤ 5.

3. The negative electrode sheet according to claim 2, characterized in that, The mass fraction M1 of the first metal particles in the storage layer ranges from 20% to 70%, and the mass fraction M2 of the second metal particles in the buffer layer ranges from 9% to 50%.

4. The negative electrode sheet according to claim 1, characterized in that, The ratio of the mass fraction C1 of the first carbon particles to the mass fraction M1 of the first metal particles in the storage layer is in the range of 0.5 ≤ C1 / M1 ≤ 3.

5.

5. The negative electrode sheet according to claim 1, characterized in that, The ratio of the specific mass of the second carbon particle to the specific mass of the first carbon particle is less than or equal to 0.

6.

6. The negative electrode sheet according to claim 1, characterized in that, The median particle size of the first carbon particle ranges from 2 μm to 50 μm; the median particle size of the second carbon particle ranges from 10 nm to 500 nm.

7. The negative electrode sheet according to claim 1, characterized in that, The thickness of the storage layer ranges from 20 μm to 100 μm, and the thickness of the buffer layer ranges from 1 μm to 20 μm.

8. The negative electrode sheet according to claim 1, characterized in that, The first metal particle includes at least one of Mg, Sn, Ag, In, Zn, Al, Fe, Ga, Sb, Bi, Au, and Pt; the second metal particle includes at least one of Mg, Sn, Ag, In, Zn, Al, Fe, Ga, Sb, Bi, Au, and Pt.

9. The negative electrode sheet according to claim 6, characterized in that, The first carbon particle includes at least one of natural graphite, artificial graphite, hard carbon, soft carbon, and micron-sized porous carbon; the second carbon particle includes at least one of acetylene black, Ketjen black, and super carbon black.

10. A solid-state battery, characterized in that, include: Solid electrolyte, Positive electrode sheets are stacked on the surface of the solid electrolyte, and The negative electrode sheet according to any one of claims 1 to 9, wherein the negative electrode sheet is stacked on the surface of the solid electrolyte opposite to the positive electrode sheet, wherein the buffer layer is disposed between the solid electrolyte and the storage layer.

11. An electrical appliance, characterized in that, include: The main body of the electrical equipment; and The solid-state battery of claim 10 is used to power the electrical device body.

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