Solid-state battery

Abstract

The application discloses a solid-state battery. The solid-state battery comprises a positive electrode sheet, a solid-state electrolyte layer and a negative electrode sheet which are arranged in a stack, the positive electrode sheet comprises a positive electrode tab, the negative electrode sheet comprises a negative electrode tab, at least part of the positive electrode tab and / or the negative electrode tab is covered with the solid-state electrolyte layer, the positive electrode sheet comprises lithium cobaltate particles, and the lithium cobaltate particles have an O2 phase crystal structure. The application selects O2 phase lithium cobaltate, and covers at least part of the positive electrode tab and / or at least part of the negative electrode tab with the solid-state electrolyte layer, so that the lattice distortion and phase transition of the O2 phase lithium cobaltate under the working voltage can be effectively inhibited while ensuring high energy density of the battery, sufficient lithium ion migration channels are provided, the ion transmission path is optimized, the problem of burrs and lithium dendrites generated by stress concentration of the electrode tab is improved, the risk of internal short circuit is reduced, and the battery has excellent rate performance and cycle stability.

Description

Technical Field

[0001] This application belongs to the field of batteries, specifically relating to a solid-state battery. Background Technology

[0002] O2-phase lithium cobalt oxide with space group P63mc possesses wider ion channels and a higher theoretical lithium-ion diffusion coefficient (10⁻¹⁰) due to its hexagonal layered structure. -10 -10 -9 cm 2 Theoretically, this gives it the potential to achieve high-rate charge and discharge and high energy density. However, in liquid battery systems, the O2 phase lithium cobalt oxide is limited by electrolyte decomposition under high voltage and phase structure instability under conventional voltage, making it difficult to effectively realize its theoretical performance advantages.

[0003] Using solid-state electrolytes, especially oxide / halide electrolytes, to construct all-solid-state batteries can avoid the negative impacts caused by electrolyte oxidation and decomposition. Furthermore, the rigid structure of oxide / halide electrolytes can suppress lattice distortion and phase transitions of O2-phase lithium cobalt oxide under conventional voltages, opening up possibilities for the application of O2-phase lithium cobalt oxide. However, existing O2-phase lithium cobalt oxide solid-state batteries still face the problem of unsatisfactory cycle life. Summary of the Invention

[0004] Therefore, the technical problem to be solved by this application is to overcome the short cycle life of solid-state batteries using O2 phase lithium cobalt oxide in the prior art, thereby providing a battery with good cycle stability.

[0005] To achieve the above objectives, this application provides the following technical solutions.

[0006] According to an embodiment of this application, a solid-state battery is provided, comprising a positive electrode, a solid electrolyte layer, and a negative electrode stacked together. The positive electrode includes a positive current collector, a positive active layer, and at least one positive tab. The positive active layer is disposed on at least one surface of the positive current collector in the thickness direction. The positive tab extends from the positive current collector, and its extension direction is perpendicular to the thickness direction of the positive current collector. The negative electrode includes a negative current collector, a negative active layer, and at least one negative tab. The negative active layer is disposed on at least one surface of the negative current collector in the thickness direction. The negative tab extends from the negative current collector, and its extension direction is perpendicular to the thickness direction of the negative current collector. At least a portion of the positive tab and / or the negative tab is covered by the solid electrolyte layer, which includes at least one of a first oxide electrolyte and a first halide electrolyte. The positive active layer includes a positive active material, which includes lithium cobalt oxide particles having an O2 phase crystal structure and the chemical formula Li.x Na y Co k M z O2, M includes at least one element selected from Mg, Al, Ti, Zr, Ni, Mn, F, Y, Nb, La, B, and W, with 0.82≤x<1, 0.005≤y≤0.08, 0.8≤k≤1.05, and 0.005≤z≤0.04.

[0007] In some optional embodiments, the thickness direction of the negative electrode current collector is a first direction, the extension direction of the negative electrode tab is a second direction, and a third direction is perpendicular to both the first and second directions. Along the second direction, the length of the positive electrode tab is Le1, and the length of the solid electrolyte layer covering the positive electrode tab is Ls1, satisfying: 0.1Le1≤Ls1≤0.7Le1; along the third direction, the length of the positive electrode tab is We1, and the length of the solid electrolyte layer covering the positive electrode tab is Ws1, satisfying: 0.1We1≤Ws1≤We1.

[0008] In some alternative embodiments, along the second direction, the length of the negative electrode tab is Le2, and the length of the solid electrolyte layer covering the negative electrode tab is Ls2, satisfying: 0.1Le2≤Ls2≤0.7Le2; along the third direction, the length of the negative electrode tab is We2, and the length of the solid electrolyte layer covering the negative electrode tab is Ws2, satisfying: 0.1We2≤Ws2≤We2.

[0009] Furthermore, in some alternative implementations, the following condition is satisfied: 0.3Le1≤Ls1≤0.6Le1.

[0010] Furthermore, in some alternative implementations, the following condition is satisfied: 0.3Le2≤Ls2≤0.6Le2.

[0011] In some alternative embodiments, along the first direction, the length of the positive electrode tab is Te1, and the length of the solid electrolyte layer covering the positive electrode tab is Ts1, satisfying: 5Te1≤Ts1≤20Te1.

[0012] In some alternative embodiments, along the first direction, the length of the negative electrode tab is Te2, and the length of the solid electrolyte layer covering the negative electrode tab is Ts2, satisfying: 5Te2≤Ts2≤20Te2.

[0013] In some optional embodiments, the area of ​​the positive electrode tab perpendicular to the first direction is S1, and the area of ​​the solid electrolyte layer covering the positive electrode tab is S2, satisfying: 0.03≤S2 / S1≤0.6.

[0014] In some optional embodiments, the area of ​​the negative electrode tab perpendicular to the first direction is S3, and the area of ​​the solid electrolyte layer covering the negative electrode tab is S4, satisfying: 0.03≤S4 / S3≤0.6.

[0015] In some alternative embodiments, the porosity of the solid electrolyte layer is less than or equal to 5%.

[0016] In some alternative embodiments, the thickness of the solid electrolyte layer is 10 μm-500 μm.

[0017] Furthermore, in some optional embodiments, the thickness of the solid electrolyte layer is 100μm-500μm.

[0018] In some alternative embodiments, the solid electrolyte layer comprises a blend of the first oxide electrolyte and the first halide electrolyte, wherein the mass content of the first oxide electrolyte is 40%-50% and the mass content of the first halide electrolyte is 50%-60% based on the mass of the solid electrolyte layer.

[0019] In some optional embodiments, the solid electrolyte layer includes a first electrolyte layer and a second electrolyte layer stacked together, the first electrolyte layer being close to the negative electrode and having a thickness of 5μm-150μm, and the second electrolyte layer being close to the positive electrode and having a thickness of 5μm-350μm.

[0020] Furthermore, in some alternative embodiments, the first electrolyte layer comprises the first oxide electrolyte, and the second electrolyte layer comprises the first halide electrolyte.

[0021] Furthermore, in some alternative embodiments, the first electrolyte layer comprises a sulfide electrolyte, and the second electrolyte layer comprises at least one of the first oxide electrolyte and the first halide electrolyte.

[0022] In some optional embodiments, the lithium cobalt oxide particles are in the form of sheets, with a plane perpendicular to their thickness direction as the projection surface. The orthographic projection of the lithium cobalt oxide particles on the projection surface has a minor diameter A μm. The direction of the line connecting the two farthest points in the outer contour of the orthographic projection is the fourth direction, and the direction perpendicular to the fourth direction is the fifth direction. The minor diameter A μm is the length of the orthographic projection along the fifth direction and perpendicularly bisects the fourth direction, satisfying: 1≤A≤10.

[0023] Furthermore, in some optional embodiments, the orthographic projection of the lithium cobalt oxide particle on the projection plane also has a major diameter B μm, wherein the major diameter B μm is the length of the orthographic projection along the fourth direction, satisfying: 5≤B / A≤40.

[0024] In some optional embodiments, at least a portion of the surface of the lithium cobalt oxide particles has a coating layer with a thickness of 5 nm to 50 nm, the coating layer comprising at least one of a second oxide electrolyte and a second halide electrolyte.

[0025] In some alternative embodiments, the thickness of the lithium cobalt oxide particles is 0.1 μm-1 μm.

[0026] In some optional embodiments, the particle size Dv50 of the lithium cobalt oxide particles is 0.1 μm-20 μm.

[0027] Furthermore, in some optional embodiments, the particle size Dv50 of the lithium cobalt oxide particles is 0.1 μm-10 μm.

[0028] In some optional embodiments, the X-ray diffraction pattern of the lithium cobalt oxide particles shows diffraction peaks at 2θ positions of 18.0°-18.9°, 37.4°-38°, 57.7°-58.3°, 36.6°-37.2°, 37.9°-38.5°, and 66.3°-66.9°.

[0029] Furthermore, in some optional embodiments, 2θ belongs to the diffraction peak of the (002) crystal plane in the range of 18.0°-18.9°, and the intensity of the diffraction peak of the (002) crystal plane is I(002). 2θ belongs to the diffraction peak of the (110) crystal plane in the range of 66.3°-66.9°, and the intensity of the diffraction peak of the (110) crystal plane is I(110), satisfying: 3≤I(002) / I(110)≤15.

[0030] Furthermore, in some alternative implementations, the following condition is satisfied: 5≤I(002) / I(110)≤10.

[0031] In some alternative embodiments, the first oxide electrolyte and the second oxide electrolyte each independently comprise Li m Al n Ti q (PO4)3, Li7La3Zr2O 12 Li w La v At least one of TiO3, wherein 1.3≤m≤1.5, 0.3≤n≤0.5, 1.5≤q≤1.7, 0.3≤w≤0.5, and 0.9≤v≤1.0.

[0032] In some alternative embodiments, the particle size Dv50 of the first oxide electrolyte is 50 nm-1000 nm.

[0033] Furthermore, in some optional embodiments, the particle size Dv50 of the first oxide electrolyte is 100nm-500nm.

[0034] In some optional embodiments, the first halide electrolyte and the second halide electrolyte each independently comprise Li3QCl6, where Q comprises at least one element selected from In, Y, Er, Ti, Al, Zr, and Ta. In some optional embodiments, the particle size Dv50 of the first halide electrolyte is 50 nm to 1500 nm.

[0035] Furthermore, in some optional embodiments, the particle size Dv50 of the first halide electrolyte is 200nm-800nm.

[0036] In some alternative embodiments, the sulfide electrolyte has the general chemical formula Li. b A e T d Z c X a , 1≤a≤1.5, 5.5≤b≤7, 0≤c≤1, 3.5≤d≤5, 0≤e≤1, A includes at least one of P, As, and Sb, T includes at least one of Si and Ge, Z includes at least one of O and Se, and X includes at least one of Cl, Br, and I.

[0037] In some optional embodiments, the negative electrode includes a negative electrode active layer comprising lithium metal, and the areal capacity of the negative electrode active layer is 4 mAh / cm². 2 -8mAh / cm 2 .

[0038] The technical solution of this application has the following advantages: The solid-state battery provided in this application includes a positive electrode, a solid electrolyte layer, and a negative electrode stacked together. The positive electrode includes a positive current collector, a positive active layer, and at least one positive tab. The positive active layer is disposed on at least one surface of the positive current collector along its thickness direction. The positive tab extends from the positive current collector, and its extension direction is perpendicular to the thickness direction of the positive current collector. The negative electrode includes a negative current collector, a negative active layer, and at least one negative tab. The negative active layer is disposed on at least one surface of the negative current collector along its thickness direction. The negative tab extends from the negative current collector, and its extension direction is perpendicular to the thickness direction of the negative current collector. At least a portion of the positive tab and / or the negative tab is covered by the solid electrolyte layer, which includes at least one of a first oxide electrolyte and a first halide electrolyte. The positive active layer includes a positive active material, and the lithium cobalt oxide particles have an O2 phase crystal structure with the chemical formula Li. x Na y Co k M z O2, M includes at least one element selected from Mg, Al, Ti, Zr, Ni, Mn, F, Y, Nb, La, B, and W, with 0.82≤x<1, 0.005≤y≤0.08, 0.8≤k≤1.05, and 0.005≤z≤0.04.

[0039] This application selects O2-phase lithium cobalt oxide with the above-mentioned chemical composition, and makes the solid electrolyte layer cover at least part of the positive tab and / or at least part of the negative tab. In this way, while ensuring the high energy density of the battery, it can effectively suppress the lattice distortion and phase transformation of O2-phase lithium cobalt oxide under the working voltage, and also provide sufficient lithium ion migration channels, optimize ion transport paths, and improve the problem of burrs and lithium dendrites caused by stress concentration under the influence of extrusion or cycle volume change of the tab, reduce the risk of internal short circuit, so that the battery has both excellent rate performance and cycle stability. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the negative electrode current collector and negative electrode tab in one embodiment of this application; Figure 2 This is a schematic diagram of the electrolyte membrane structure in one embodiment of this application; Figure 3 This is a schematic diagram of the structure of a negative electrode sheet with a solid electrolyte layer transferred in one embodiment of this application; Figure 4 yes Figure 3 Side view; Figure 5 This is a schematic diagram of the battery structure in one embodiment of this application; Figure 6 This is an X-ray diffraction pattern of lithium cobalt oxide particles in one embodiment of this application; Figure 7 This is a scanning electron microscope image of lithium cobalt oxide particles in one embodiment of this application.

[0042] The reference numerals in the attached figures are explained as follows: 11-Positive current collector; 12-Positive active layer; 21-Negative current collector; 22-Negative active layer; 23-Negative tab; 30-Solid electrolyte layer. Detailed Implementation

[0043] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0044] It should be noted in the description of this application that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the technical features involved in the different embodiments of this application described below may be combined with each other as long as they do not conflict with each other.

[0045] This study found that during the subsequent cycling of all-solid-state batteries, the tab area of ​​the electrode is a high-risk area for stress concentration and structural defects, especially the tab of the lithium metal anode. Under the influence of compression or cyclic volume changes, burrs or lithium dendrites are easily formed. These sharp lithium dendrites can pierce the passivation layer on the tab surface and become active conductive sites. Since the solid electrolyte layer only covers the edge of the active area of ​​the electrode, the root of the tab (i.e., the end where the tab connects to the electrode) is exposed, posing a potential risk of contact with the counter electrode. The formation of lithium dendrites further reduces the distance between the tab and the counter electrode, and may even directly pierce the tiny gap between the electrodes to form a conductive path, significantly increasing the probability of internal short circuits, thereby leading to a significant reduction in the cycle life of the battery.

[0046] In addition, there are several challenges in applying O2-phase lithium cobalt oxide to all-solid-state batteries: First, the thermal expansion coefficients of O2-phase lithium cobalt oxide and oxide / halide electrolytes do not match, which can easily lead to microcracks during battery fabrication or cycling, affecting interface integrity. Furthermore, the ionic conductivity of oxide electrolytes decreases significantly at low temperatures, limiting the low-temperature cycling performance of the battery. Second, the morphology of conventional O2-phase lithium cobalt oxide is difficult to ideally match the layered ion channels in its P63mc space group, resulting in an extended lithium-ion diffusion path and increased interfacial impedance between the cathode and electrolyte, thus limiting the rate performance of the battery. Third, the structural stability of O2-phase lithium cobalt oxide under high-voltage deep delithiation conditions is insufficient, which limits the improvement of battery energy density.

[0047] To address the problems of insufficient cycle life, poor rate and low-temperature performance, and unsatisfactory energy density in solid-state batteries using O2-phase lithium cobalt oxide in related technologies, this application proposes the following solutions.

[0048] According to an embodiment of this application, a solid-state battery is provided, comprising a positive electrode, a solid electrolyte layer, and a negative electrode stacked together. The positive electrode includes a positive current collector, a positive active layer, and at least one positive tab. The positive active layer is disposed on at least one surface of the positive current collector in the thickness direction. The positive tab extends from the positive current collector, and its extension direction is perpendicular to the thickness direction of the positive current collector. The negative electrode includes a negative current collector, a negative active layer, and at least one negative tab. The negative active layer is disposed on at least one surface of the negative current collector in the thickness direction. The negative tab extends from the negative current collector, and its extension direction is perpendicular to the thickness direction of the negative current collector. At least a portion of the positive tab and / or the negative tab is covered by the solid electrolyte layer, which includes at least one of a first oxide electrolyte and a first halide electrolyte. The positive active layer includes a positive active material, which includes lithium cobalt oxide particles having an O2 phase crystal structure and the chemical formula Li. x Na y Co k M z O2, M includes at least one element selected from Mg, Al, Ti, Zr, Ni, Mn, F, Y, Nb, La, B, and W, with 0.82≤x<1, 0.005≤y≤0.08, 0.8≤k≤1.05, and 0.005≤z≤0.04.

[0049] Based on the foregoing analysis, it is evident that exposed tab roots are highly susceptible to internal short circuits when lithium dendrites form. Therefore, this application extends the solid electrolyte layer to cover the tab roots, meaning that at least a portion of the positive and / or negative tabs is covered by a solid electrolyte layer. This creates a gradual current distribution at the tab-electrolyte interface, preventing localized overheating and interface degradation caused by concentrated current density. Simultaneously, the solid electrolyte covering the tab roots acts as an ion buffer, regulating the uniform distribution of ion flow during charging and discharging, alleviating interfacial stress in the tab region, and thus improving issues such as burrs and lithium dendrites caused by stress concentration on the tabs. This reduces the risk of internal short circuits and significantly enhances the battery's cycle performance.

[0050] This study found that the molar content (x) of lithium in the O2 phase lithium cobalt oxide directly affects the ion channel accessibility and lattice stability of the material. By controlling the value of x within the range of ≥0.82 and <1, sufficient lithium-ion migration channels can be provided while maintaining the stability of the lithium cobalt oxide crystal structure, without relying on the wetting effect of the liquid electrolyte to construct lithium-ion transport paths. This is beneficial for the rapid transport of lithium ions in solid-state batteries, thereby balancing the rate performance and cycle stability of the battery. When x < 0.82, it indicates insufficient lithium content, resulting in a sharp reduction in lithium-ion migration channels, hindered ion transport, and decreased battery rate performance. Conversely, when x > 1, excessive lithium can easily induce lattice distortion, which also leads to blockage of ion transport channels, reduced lithium-ion diffusion rate, and deterioration of battery rate performance.

[0051] The molar content (y) of sodium in the O2 phase lithium cobalt oxide is related to the optimization of the lithium-ion diffusion path at the cathode-solid electrolyte interface and in the bulk phase. By controlling the value of y within the range of 0.005-0.08, the lithium-ion diffusion rate in the layered structure of lithium cobalt oxide and at the cathode-solid electrolyte interface can be improved, thus enhancing ion conduction performance. If y < 0.005, the amount of sodium doping is too small, which cannot optimize the ion transport path, resulting in no significant improvement in rate performance. Conversely, if y > 0.08, excessive sodium will occupy lithium-ion sites, hindering lithium-ion migration and weakening rate performance.

[0052] By introducing the element M into the crystal structure of O2-phase lithium cobalt oxide and controlling the molar content of M, z, between 0.005 and 0.04, lattice distortion and structural stability can be effectively suppressed. Since solid-state batteries commonly suffer from poor solid-solid interface contact, the stress generated during the volume change of lithium cobalt oxide particles during lithium delithiation / intercalation cannot be effectively released, leading to easier crack formation and propagation, thus exacerbating structural distortion and failure. If z < 0.005, the amount of M doping is too small, making it difficult to suppress the Jahn-Teller distortion of Co ions in lithium cobalt oxide, resulting in increased interface impedance and affecting rate performance. Conversely, if z > 0.04, excessive M not only reduces active sites, leading to a decrease in the theoretical specific capacity and actual discharge capacity of the battery, but also disrupts the continuity of the layered structure, similarly hindering lithium-ion conduction and reducing rate performance.

[0053] In summary, this application selects O2-phase lithium cobalt oxide with the above-mentioned chemical composition and uses it in combination with an oxide / halide electrolyte layer that can at least partially cover the root of the tab. This can effectively suppress the lattice distortion and phase transition of O2-phase lithium cobalt oxide under the working voltage while ensuring the high energy density of the battery. It can also provide sufficient lithium-ion migration channels, optimize the ion transport path, and improve the problem of burrs and lithium dendrites caused by stress concentration under the influence of extrusion or cycle volume changes on the tab. This reduces the risk of internal short circuit, thus enabling the battery to have both excellent rate performance and cycle stability.

[0054] It should be noted that the chemical formula of the O2 phase lithium cobalt oxide particles is Li x Na y Co k M z The stoichiometric coefficients x, y, z, and k in O2 can be determined using bulk chemical analysis methods. The specific testing steps are as follows: After removing the battery's encapsulation film, locate the positive electrode active material layer region according to the positive electrode tab, cut a positive electrode sheet sample from that region, remove the current collector, and obtain the positive electrode active material layer powder. Place the obtained powder sample in a vacuum drying oven and dry it for 10 hours at a temperature range of 80-120℃ to completely remove adsorbed moisture. Accurately weigh the dried sample using an analytical balance with an accuracy of 0.1 mg, and record the mass as m. 初The weighed sample was placed in a digestion vessel and submerged in an aqua regia system prepared by a 3:1 volume ratio of concentrated hydrochloric acid and concentrated nitric acid. After standing for 30 minutes until the vigorous reaction subsided, approximately 1 / 5 volume of hydrofluoric acid (approximately 40% concentration) was added, and the mixture was allowed to stand for another 30 minutes. Finally, approximately 1 / 10 volume of hydrogen peroxide (approximately 30% concentration) was added to promote the decomposition of organic components. The sealed digestion vessel was placed in a microwave digester, and a gradient temperature program was set to increase the temperature to 210°C at a rate of 3°C / min and maintain this temperature for 30 minutes to achieve complete sample digestion under high temperature and high pressure conditions. The inner wall of the digestion vessel and the transfer container were repeatedly rinsed with a 2-5% dilute nitric acid solution. All washings were combined and transferred to a polypropylene or polyethylene plastic volumetric flask, and the volume was adjusted to the standard volume (e.g., 50 mL) with dilute nitric acid and thoroughly mixed to obtain the mother liquor for analysis. Based on the linear range of the ICP instrument and the expected concentrations of each element, the mother liquor was diluted appropriately with 2% nitric acid solution to prepare a series of solutions with the required concentration range for instrument testing. Using ICP-OES or ICP-MS instruments, characteristic spectral lines of lithium (Li), cobalt (Co), sodium (Na), and dopant elements M (Mg, Al, Ti, etc.) were selected for determination to obtain the concentration value (Celement, unit: μg / mL) of each element in the test solution. The mass fraction of each element in the cathode material was calculated using the following formula: Celement (μg / g) = Celement × Vtotal / m 初 Where Vtotal is the total constant volume (mL), m 初 The initial sample mass is (g). After converting the mass fraction of each element into a molar ratio, the stoichiometric coefficients of x, y, z, and k in the chemical formula can be obtained.

[0055] For ease of description, in this application, the thickness direction of the negative electrode current collector is defined as the first direction, the extension direction of the negative electrode tab is defined as the second direction, and a third direction is perpendicular to both the first and second directions. It is understood that, in one embodiment of this application, the solid electrolyte layer includes a body and a protrusion, the protrusion extending from the body and covering at least a portion of the positive electrode tab and / or at least a portion of the negative electrode tab. The following is in conjunction with... Figures 1 to 5 The following explanation will be based on the example of a negative electrode covered by a solid electrolyte layer.

[0056] Please see Figure 1 Along the second direction, the length of the negative electrode tab is Le2, and along the third direction, the length of the negative electrode tab is We2. See also... Figure 2 Along the second direction, the solid electrolyte layer covers the negative electrode tab for a length of Ls2, and along the third direction, the solid electrolyte layer covers the negative electrode tab for a length of Ws2.

[0057] like Figure 3 As shown, this application controls the value of Ls2 to be between 0.1Le2 and 0.7Le2, and further between 0.3Le2 and 0.6Le2, and the value of Ws2 to be between 0.1We2 and We2. This ensures that the solid electrolyte layer fully covers the high-stress area at the root of the negative electrode, effectively alleviates the interfacial stress in this area, reduces the generation of burrs and lithium dendrites from the source, and thus significantly reduces the risk of internal short circuit in the battery and improves the cycle performance of the battery.

[0058] If Ls2 < 0.1Le2 or Ws2 < 0.1We2, it indicates that the coverage area of ​​the solid electrolyte layer is too small, which cannot effectively improve the problem of burrs and lithium dendrites formed at the root of the tab due to stress concentration, thus making it difficult to improve the cycle performance of the battery. Conversely, if Ls2 > 0.7Le2 or Ws2 > We2, it means that the coverage area of ​​the solid electrolyte layer is too large. This not only increases the amount of electrolyte material used, but also introduces unnecessary interfacial contact resistance, hindering lithium-ion transport efficiency, which is also detrimental to improving the cycle performance of the battery.

[0059] Ls2 and Le2 can be independently obtained by measuring with a digital or analog outside micrometer. For example, the value of Ls2 can be 0.1Le2, 0.2Le2, 0.3Le2, 0.33Le2, 0.36Le2, 0.39Le2, 0.42Le2, 0.45Le2, 0.48Le2, 0.51Le2, 0.54Le2, 0.57Le2, 0.6Le2, 0.7Le2, etc., or values ​​within any two of the above values. Le2 can be, for example, 1mm-20mm, preferably 8mm-20mm. As an example, Le2 can be 1mm, 3mm, 5mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, etc., or values ​​within any two of the above values.

[0060] Ws2 and We2 can be independently measured using a digital or analog outside micrometer. For example, the value of Ws2 can be 0.1We2, 0.2We2, 0.3We2, 0.4We2, 0.5We2, 0.6We2, 0.7We2, 0.8We2, 0.9We2, 1.0We2, or a value within any range of two of the above values. We2 can be, for example, 1-20 mm, preferably 4 mm-12 mm. As an example, We2 can be 1 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, or a value within any range of two of the above values.

[0061] It should be noted that the solid-state battery in this application adopts a multi-layer stacked structure, that is, stacked in the order of first electrode - solid electrolyte layer - second electrode - solid electrolyte layer - first electrode - solid electrolyte layer... solid electrolyte layer - second electrode - solid electrolyte layer - first electrode. Therefore, the first and last stacked first electrode layers are both outermost electrode layers. The first and second electrodes sandwiched between the outermost electrode layers (with opposite polarity to the first electrode layer) are called inner electrode layers. To improve the energy density of the battery, the inner electrode layers usually have active layers on both sides of their thickness direction, while the outermost electrode layers only have active layers on the surface of their side facing the electrode stacking direction (the battery thickness direction). It can be understood that the inner electrode layers include double-sided positive electrode sheets and double-sided negative electrode sheets.

[0062] In one embodiment of this application, the electrolyte membrane includes a polymer base film and a solid electrolyte layer disposed on one surface of the polymer base film. Using a transfer printing technique, the solid electrolyte layer on the electrolyte membrane is transferred to the surface of the active layer of the double-sided negative electrode, forming a membrane as described above. Figure 4 The structure shown is followed by the stacking of double-sided positive electrode plates on both sides of the structure, and then stacking on both sides of the double-sided positive electrode plates. Figure 4 The structure shown is repeated with the steps described above. Please participate. Figure 5 Until the solid-state battery assembly is completed.

[0063] Along the first direction (electrode stacking direction), the length of the negative electrode tab is Te2, and the length of the solid electrolyte layer covering the negative electrode tab is Ts2, satisfying: 5Te2≤Ts2≤20Te2. By controlling Ts2 between 5 and 20 times Te2, a suitable thickness of the solid electrolyte layer can be ensured. This not only effectively improves problems such as burrs and lithium dendrites caused by stress concentration in the electrode tab, significantly reducing the risk of short circuits within the battery, but also prevents the solid electrolyte layer from being too thick, which would increase lithium-ion transport resistance and reduce the proportion of active material, thereby affecting the battery's energy performance and rate capability.

[0064] Te2 and Ts2 can be obtained independently using a digital outside micrometer or a pointer outside micrometer. For example, the value of Ts2 can be 5.0Te2, 6.5Te2, 8.0Te2, 9.5Te2, 11.0Te2, 12.5Te2, 14.0Te2, 15.5Te2, 17.0Te2, 18.5Te2, 20.0Te2, or a value within any two of the above values. Te2 can be, for example, 2μm-30μm. As an example, Te2 can be 2μm, 5μm, 8μm, 11μm, 14μm, 17μm, 20μm, 23μm, 26μm, 29μm, 30μm, or a value within any two of the above values.

[0065] In some embodiments, the area of ​​the negative electrode tab perpendicular to the first direction is S3, and the area of ​​the solid electrolyte layer covering the negative electrode tab is S4, satisfying: 0.03 ≤ S4 / S3 ≤ 0.6. This provides necessary protection for the negative electrode tab while preventing excessive coverage by the solid electrolyte layer, thus balancing ion conduction efficiency and cycle performance. If S4 / S3 < 0.03, it indicates insufficient coverage of the root of the negative electrode tab by the solid electrolyte layer, making it difficult to improve lithium dendrite growth and internal short-circuit risk; conversely, if S4 / S3 > 0.6, it increases electrolyte redundancy and interface impedance, which is detrimental to improving rate capability and cycle performance.

[0066] For example, the values ​​of S4 / S3 can be 0.03, 0.09, 0.14, 0.20, 0.26, 0.31, 0.37, 0.43, 0.48, 0.54, 0.60, etc., or values ​​within the range of any two of the above values.

[0067] It is understood that when the solid electrolyte layer covers part of the positive electrode tab, the length of the covered area also satisfies at least one of the above conditions, namely: along the second direction, the length of the positive electrode tab is Le1, and the length of the solid electrolyte layer covering the positive electrode tab is Ls1, satisfying: 0.1Le1≤Ls1≤0.7Le1; preferably 0.3Le1≤Ls≤0.6Le1; along the third direction, the length of the positive electrode tab is We1, and the length of the solid electrolyte layer covering the positive electrode tab is Ws1, satisfying: 0.1We1≤Ws1≤We1; along the first direction, the length of the positive electrode tab is Te1, and the length of the solid electrolyte layer covering the positive electrode tab is Ts1, satisfying: 5Te1≤Ts1≤20Te1; the area of ​​the positive electrode tab perpendicular to the first direction is S1, and the area of ​​the solid electrolyte layer covering the positive electrode tab is S2, satisfying: 0.03≤S2 / S1≤0.6.

[0068] In this application, the lengths of the positive electrode tab and the negative electrode tab can be the same or different in the first, second, and third directions, depending on the actual needs.

[0069] In some implementations, a transfer technology is used to transfer the solid electrolyte layer on the electrolyte membrane to the active layer surface of the double-sided positive electrode. Then, double-sided negative electrodes are stacked on both sides, and double-sided positive electrodes with the solid electrolyte layer transferred are stacked on both sides of the double-sided negative electrodes. The aforementioned steps are repeated until the assembly of the solid-state battery is completed.

[0070] Furthermore, when the solid electrolyte layer simultaneously covers both the positive and negative electrode tabs, the solid electrolyte layer on the electrolyte membrane can be transferred to the active layer surface of the double-sided positive electrode to form a double-sided positive electrode with a transferred solid electrolyte layer. Similarly, the solid electrolyte layer on the electrolyte membrane can be transferred to the active layer surface of the double-sided negative electrode to form a double-sided negative electrode with a transferred solid electrolyte layer. These are then stacked in a positive-negative-positive order until the solid-state battery assembly is complete. Accordingly, the length of the coverage area of ​​the solid electrolyte layer satisfies the aforementioned conditions, which will not be elaborated further here.

[0071] In some embodiments, by controlling the porosity of the solid electrolyte layer to be less than or equal to 5%, the electrolyte layer structure can be made more compact, effectively shortening the lithium-ion transport path, improving the bulk and interfacial ionic conductivity, and simultaneously enhancing the mechanical strength of the electrolyte layer and its ability to suppress dendrite growth, thereby improving the rate performance, cycle stability, and safety of the battery. For example, the porosity of the solid electrolyte layer can be 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, or a value within any two of the above ranges.

[0072] In this application, the porosity of the solid electrolyte layer can be changed by adjusting the particle size of the first oxide electrolyte and / or the first halide electrolyte, and the pressure used in the transfer step. This is a consensus in the art, so it will not be elaborated further.

[0073] It should be noted that the porosity of the solid electrolyte layer can be obtained by mercury intrusion porosimetry according to the national standard GB / T 21650.1-2008. The specific test involves cutting the solid electrolyte membrane into 1cm × 1cm samples, measuring the porosity at a maximum pressure of 414MPa in a fully automated mercury intrusion porosimetry instrument, analyzing the mercury intrusion curve, using the end point of the mercury intrusion curve plateau (approximately 3 psi) as the starting point for calculation, subtracting the inter-sample voids, and then calculating the volumetric porosity based on the cumulative mercury intrusion amount and the apparent volume of the sample.

[0074] In some implementations, by controlling the thickness of the solid electrolyte layer to be between 10 μm and 500 μm, and especially further between 100 μm and 500 μm, sufficient mechanical strength can be ensured to suppress dendrite growth and maintain a stable electrode / electrolyte interface, while effectively controlling the solid-state transport distance of lithium ions and the overall battery volume, thereby improving the battery's cycle stability, rate performance, and volumetric energy density. If the thickness of the solid electrolyte layer is less than 10 μm, the mechanical strength of the electrolyte layer is insufficient, making it susceptible to dendrite puncture, and the interface buffering capacity is limited; if the thickness of the solid electrolyte layer is greater than 500 μm, it will significantly increase ion transport impedance and reduce the battery's energy density.

[0075] It should be noted that the thickness of the solid electrolyte layer can be measured using the same method as the aforementioned Ts2 test, or it can be measured using a combination of ion beam cutting (CP) and scanning electron microscopy (SEM). The specific testing method includes: after removing the membrane shell of the pouch cell, taking out the area containing the solid electrolyte layer (e.g., a multi-layer sandwich structure of positive electrode / solid electrolyte layer / negative electrode), placing it on the CP equipment sample stage, locating the pre-section position under SEM, setting the cutting parameters, using a relatively low accelerating voltage of 3-6 kV (lower voltage results in a shallower damage layer but a slower cutting rate), and initially using a larger ion beam current (e.g., approximately 1 μA) for rapid coarse cutting, switching to a smaller beam current (e.g., approximately 100 kA) near the target interface. (nA) Fine polishing is performed. The cutting angle is typically set between 1-5° between the ion beam and the sample surface; a smaller angle yields a smoother cross-section. After cutting, the sample does not need to be moved. The fresh cross-section cut by the ion beam is directly observed in SEM mode on the same dual-beam electron microscope. Measurements are taken at different locations on the electrolyte membrane cross-section, recording at least 5-10 measurements, and the average thickness is calculated. For example, the thickness of the solid electrolyte layer can be 10 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, or a value within any two of the above ranges.

[0076] In some embodiments, the solid electrolyte layer includes a blend of the first oxide electrolyte and the first halide electrolyte. Based on the mass of the solid electrolyte layer, by controlling the mass content of the first oxide electrolyte to be between 40% and 50% and the mass content of the first halide electrolyte to be between 50% and 60%, the oxide electrolyte can maintain the structural stability of the electrolyte layer with its rigid framework and suppress the lattice distortion of the positive electrode active material. The halide electrolyte, on the other hand, can construct a continuous high-conductivity ion network with its low migration activation energy, and can also ensure efficient ion transport under low temperature conditions. Thus, the battery can be synergistically guaranteed to maintain structural stability, ion conduction efficiency and cycle life over a wide temperature range.

[0077] Under the premise that the total thickness of the solid electrolyte layer remains unchanged, if the mass content of the first halide electrolyte is too high (>60%), the mass content of the first oxide electrolyte will be too low (<40%). This will weaken the rigid support of the electrolyte layer, reduce mechanical strength, increase the risk of dendrite puncture, and excessive halide may exacerbate the interfacial side reaction with the electrode material, generating high-resistance products, thereby leading to a decline in cycle performance. Conversely, if the mass content of the first halide electrolyte is too low (<50%), the mass content of the first oxide electrolyte will be too high (>50%). This will make it difficult to form a continuous and high-ion conduction network, which cannot effectively compensate for the low conductivity of the oxide electrolyte at low temperatures. Lithium-ion transport is hindered, resulting in a significant decrease in the low-temperature cycle performance of the battery.

[0078] It should be noted that the mass content of the first oxide electrolyte and the first halide electrolyte can be determined by a combination of ion beam cutting (CP) and scanning electron microscopy combined with energy dispersive spectroscopy (SEM-EDS) for surface scanning. The specific testing method includes: after removing the membrane shell of the pouch cell, taking out the area containing the solid electrolyte layer (such as a multi-layer sandwich structure of positive electrode / solid electrolyte layer / negative electrode), placing it on the CP equipment sample stage, locating the pre-section position under SEM, setting the cutting parameters, using a relatively low accelerating voltage of 3-6 kV (lower voltage results in a shallower damage layer but a slower cutting rate), and initially using a larger beam current (e.g., approximately 1 μA) for rapid coarse cutting, switching to a smaller beam current (e.g., approximately 100 kA) when approaching the target interface. nA) Fine polishing is performed. Cutting angle: The angle between the ion beam and the sample surface is usually set between 1-5°. A smaller angle can obtain a smoother cross section. After cutting, there is no need to move the sample. The fresh cross section cut by the ion beam can be directly observed in the SEM-EDS mode of the same dual-beam electron microscope. Elemental quantitative analysis of specific regions is performed using EDS energy spectroscopy. Oxide electrolytes are usually rich in specific metals (such as Li, La, Zr, Ti, etc.) and halogens (Cl, Br, I) and possible metal elements (such as Y, Er, etc.) in halide electrolytes. The EDS software will give the atomic percentage of each element in the selected region. The mass percentage of the target electrolyte phase in the solid electrolyte layer can be calculated by stoichiometric normalization. For example, the mass content of the first oxide electrolyte may be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or a value within the range of any two of the above values; the mass content of the first halide electrolyte may be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, or a value within the range of any two of the above values.

[0079] In some embodiments, the solid electrolyte layer includes a first electrolyte layer and a second electrolyte layer stacked together. The first electrolyte layer is close to the negative electrode and has a thickness of 5 μm-150 μm. The second electrolyte layer is close to the positive electrode and has a thickness of 5 μm-350 μm. The first electrolyte layer includes the first oxide electrolyte, and the second electrolyte layer includes the first halide electrolyte. Thus, the halide electrolyte layer near the positive electrode, with its low migration activation energy and high ionic conductivity, can directly serve as the "low-temperature Li" electrolyte on the positive electrode side. + The "transmission bridge" efficiently activates the low-temperature electrochemical activity of O2 phase lithium cobalt oxide; while the oxide electrolyte layer near the negative electrode acts as a physical isolation layer. With its chemical inertness and rigid framework structure, it spatially blocks the interface side reaction pathways between halides and lithium metal, inhibits lithium dendrites from piercing the electrolyte layer, thereby ensuring the safety of the interface and maintaining a stable ion transport pathway, thus significantly improving the low-temperature cycle life of the battery.

[0080] If the first electrolyte layer is too thick (>150μm), the second electrolyte layer will be too thin (<5μm), which will make it difficult to form a continuous and effective high ionic conductivity network, thus affecting the low-temperature electrochemical performance of the battery. Conversely, if the second electrolyte layer is too thick (>350μm), the first electrolyte layer will be too thin (<5μm), which will weaken its physical isolation and mechanical support, which is not conducive to suppressing dendrite growth and stabilizing the interface.

[0081] In other embodiments, the first electrolyte layer comprises a sulfide electrolyte having the general chemical formula Li. b A e T d Z c X aThe following parameters are provided: 1≤a≤1.5, 5.5≤b≤7, 0≤c≤1, 3.5≤d≤5, 0≤e≤1; A includes at least one of P, As, and Sb; T includes at least one of Si and Ge; Z includes at least one of O and Se; X includes at least one of Cl, Br, and I; the second electrolyte layer includes at least one of oxide electrolyte and halide electrolyte. This allows the sulfide electrolyte layer near the negative electrode to form a lower impedance and tighter contact ion transport interface with the lithium metal negative electrode due to its extremely high ionic conductivity and good interface wettability. Its excellent flexibility effectively buffers the volumetric stress during lithium deposition / stripping, suppressing interface crack formation and significantly improving the cycle stability of the negative electrode interface. The second electrolyte layer near the positive electrode, if an oxide electrolyte is used, can provide structural support for the O2 phase lithium cobalt oxide under high pressure with its rigid framework, suppressing lattice distortion of the positive electrode material. If a halide electrolyte is used, it can serve as a "low-temperature lithium-ion transport bridge" on the positive electrode side, ensuring the electrochemical activity of the battery in low-temperature environments.

[0082] If the first electrolyte layer (sulfide) is too thick (greater than 150 μm) while the total thickness of the solid electrolyte layer remains constant, the second electrolyte layer (oxide / halide) will be too thin (less than 5 μm). In this case, although the sulfide electrolyte layer can adapt well to the volume change of the negative electrode, it will encroach on the thickness space of the second electrolyte layer, resulting in a weakened structural support when the second electrolyte layer is used as an oxide electrolyte, or difficulty in constructing continuous low-temperature ion channels when used as a halide electrolyte. At the same time, the excessively thick sulfide layer will also increase the risk of battery self-discharge due to its own certain electronic conductivity.

[0083] Conversely, if the first electrolyte layer is too thin (less than 5 μm), the second electrolyte layer will be too thick (greater than 350 μm). In this case, the sulfide layer will not be able to buffer the volume change of the negative electrode, and the interface will be prone to cracking. An excessively thick second electrolyte layer will significantly increase the ion migration resistance, limit the rate performance of the battery, and reduce the energy density of the battery.

[0084] It should be noted that the thicknesses of the first and second electrolyte layers can be measured using a combination of ion beam cutting (CP) and scanning electron microscopy (SEM). The specific testing method includes: after removing the membrane shell of the pouch cell, extracting the area containing the solid electrolyte layer (e.g., a multi-layer sandwich structure of positive electrode / solid electrolyte layer / negative electrode), placing it on the CP stage, locating the pre-section position under SEM, setting the cutting parameters, and using a relatively low accelerating voltage of 3-6 kV. Lower voltage results in a shallower damage layer to the sample, but a slower cutting rate. Initially, a larger ion beam current (e.g., approximately 1 μA) is used for rapid coarse cutting, switching to a smaller beam current (e.g., approximately 100 nA) for fine polishing near the target interface. The cutting angle is typically set between 1-5° between the ion beam and the sample surface; a smaller angle yields a smoother cross-section. After cutting, without moving the sample, the freshly cut cross-section is directly observed in SEM mode on the same dual-beam electron microscope. Measurements are taken directly at different locations on the electrolyte membrane cross-section, recording at least 5-10 measurements, and calculating the average thickness. For example, the thickness of the first electrolyte layer may be 5 μm, 20 μm, 35 μm, 50 μm, 65 μm, 80 μm, 95 μm, 110 μm, 125 μm, 140 μm, 150 μm, or a value within the range of any two of the above values; the thickness of the second electrolyte layer may be 5 μm, 40 μm, 75 μm, 110 μm, 145 μm, 180 μm, 215 μm, 250 μm, 285 μm, 320 μm, 350 μm, or a value within the range of any two of the above values.

[0085] In this application, when the solid electrolyte layer includes a first electrolyte layer and a second electrolyte layer stacked together, the porosity of the solid electrolyte layer refers to the porosity of the overall structure of the first electrolyte layer and the second electrolyte layer as a whole.

[0086] For O2-phase lithium cobalt oxide materials, the crystal structure is a hexagonal layered stack. In this structure, within the ab plane formed by the [CoO2] layers, atoms are bonded by strong covalent / ionic bonds, resulting in a stable and dense chemical bond network. This leads to a faster crystal growth rate along this direction, and the plane also serves as a two-dimensional channel for rapid lithium ion migration. Correspondingly, along the c-axis direction perpendicular to the [CoO2] layers, the layers are mainly bonded by weaker van der Waals forces or ionic bonds. The relatively weak bonding force in this direction makes the crystal prone to cleavage during growth or under external forces. Based on the above crystal anisotropy, plate-like O2-phase lithium cobalt oxide particles can be prepared through specific synthesis processes. That is, the lithium cobalt oxide particles are flat in three-dimensional space with a distinct thickness direction. In the plate-like lithium cobalt oxide particles, the large two-dimensional plane (ab plane) is parallel to the rapid ion transport plane of the crystal, while its thickness direction is roughly consistent with the c-axis direction.

[0087] Therefore, in some embodiments, controlling the short diameter Aμm within the range of 1 μm-10 μm has a clear physical significance, as it substantially limits the characteristic width of the particle in the direction parallel to its fast ion transport plane. Since lithium ions in O2-phase lithium cobalt oxide primarily migrate rapidly within the ab plane composed of [CoO2] layers, and the wide plane of the plate-like particle is parallel to this ab plane, a smaller short diameter b means a smaller lateral dimension of the particle within its fast transport plane. This increases the relative exposure area and probability of the particle's sides (crystal planes parallel to the c-axis and perpendicular to the ab plane) in the three-dimensional space of the electrode. Therefore, when lithium ions are transported from the solid electrolyte phase to the positive electrode active material, they have more opportunities to directly penetrate the particle interior from these exposed sides and then diffuse towards the particle's central region using the fast ion transport channel plane (ab plane). This optimization of the transport path shortens the average path length of lithium ions diffusing from the interface to the depths of the active material's bulk phase, thereby reducing bulk diffusion resistance and contributing to improved battery rate performance.

[0088] If the short diameter A is too large (>10 μm), it means that even if lithium ions are efficiently injected from the side, they still need to complete a longer bulk diffusion path in the ab plane. The intrinsic bulk diffusion time constant will increase, which may offset the advantage brought by the increased side exposure and limit the further improvement of the battery's rate performance.

[0089] If the short diameter A is too small (<1 μm), although the bulk diffusion path is theoretically shorter, excessive reduction in particle size will bring a series of negative effects. First, the increased specific surface area of ​​the particles will increase the risk of side reactions with the electrolyte, affecting long-term cycling stability. It will also introduce higher electronic contact resistance due to excessive interparticle interfaces, which is not conducive to further improvement of rate performance.

[0090] For example, the value of the short axis Aμm can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc., or a value within the range of any two of the above values.

[0091] Furthermore, in some embodiments, the orthographic projection of the lithium cobalt oxide particles on the projection surface also has a major diameter B μm, where B μm is the length of the orthographic projection along the fourth direction. Controlling the ratio B / A between the major diameter B and the minor diameter A between 5 and 40 allows the lithium cobalt oxide particles to maintain sufficient structural strength while possessing a sheet-like morphology conducive to ion transport. If B / A < 5, the minor diameter is relatively too long, increasing the migration path of lithium ions along the wider direction of the particle, which is detrimental to improving rate performance. If B / A > 40, the particles are too thin and elongated, lacking mechanical strength, and are prone to breakage and pulverization during electrode processing and cycling. The resulting fragments can block ion channels, similarly impairing the rate performance of the battery.

[0092] To quantitatively describe the morphology of sheet-like lithium cobalt oxide particles, further combining Figure 7 As shown, a plane perpendicular to the thickness direction is defined as the projection plane. The orthographic projection profile of the lithium cobalt oxide particle on this projection plane is used to measure the major diameter B and minor diameter A. The method for measuring the minor diameter A is as follows: First, obtain a surface SEM image of the positive electrode active material layer. In this image, select a sheet-like lithium cobalt oxide particle whose thickness direction is perpendicular to the imaging plane, and use its profile on the imaging plane as the orthographic projection profile of the particle. Next, determine the two points furthest apart in the orthographic projection profile, and define the direction connecting these two points as the fourth direction; then define the direction perpendicular to the fourth direction as the fifth direction. Finally, the length of the orthographic projection profile along the fifth direction and perpendicularly bisecting the fourth direction is determined as the minor diameter A of the lithium cobalt oxide particle, and the length of the orthographic projection profile along the fourth direction is determined as the major diameter B of the lithium cobalt oxide particle.

[0093] For example, the value of B / A can be 5.0, 7.5, 10.0, 12.5, 15.0, 17.5, 20.0, 22.5, 25.0, 27.5, 30.0, 32.5, 35.0, 37.5, 40.0, etc., or a value within the range of any two of the above values.

[0094] In some embodiments, at least a portion of the surface of the lithium cobalt oxide particles has a coating layer with a thickness of 5 nm to 50 nm. The coating layer includes at least one of a second oxide electrolyte and a second halide electrolyte. This allows the coating layer to construct a continuous high lithium-ion conduction channel on the surface of the lithium cobalt oxide particles, effectively reducing the solid-solid interface contact impedance between the positive electrode and the solid electrolyte layer, thereby reducing polarization losses during charging and discharging and improving the battery's rate performance. If the coating layer is too thin (<5 nm), it will result in incomplete coating, leaving the surface of the lithium cobalt oxide particles partially exposed, limiting the reduction of interface impedance and thus having an insignificant effect on improving rate performance. If the coating layer is too thick (>50 nm), it will increase the transport resistance of lithium ions through the coating layer, offsetting its positive effect of reducing interface impedance, which is also detrimental to improving the battery's rate performance.

[0095] It should be noted that the thickness of the coating layer on the surface of lithium cobalt oxide particles can be measured by transmission electron microscopy (TEM) and high-angle annular dark-field imaging-scanning transmission electron microscopy (HAADF-STEM). The specific testing method includes: peeling off the TEM thin film sample containing intact lithium cobalt oxide (LCO) particles from the positive electrode, ensuring that the coating layer structure is not damaged during sample preparation; and finally polishing and cleaning the sample with a low-energy ion beam to remove amorphous damage. Using a high-energy electron beam to penetrate the ultrathin sample, bright-field / dark-field images or high-resolution lattice images are formed. The contrast of the HAADF-STEM mode is sensitive to atomic number (Z contrast), which can clearly distinguish the heavy element (Co) LCO core from the light element coating layer of oxide or halide electrolytes. Under TEM / STEM, LCO particles with clear edges can be found. At the edge of the particle cross-section, high-resolution mode (HRTEM) or HAADF-STEM mode imaging can clearly show the contrast difference between the lattice fringes of the core LCO and the outer amorphous / nanocrystalline coating layer. Using the instrument's measurement software, the thickness of the coating layer should be measured directly on the image. Measurements should be taken at multiple locations on a single particle and on multiple different particles to obtain the average thickness. For example, the coating layer thickness on the surface of lithium cobalt oxide particles can be 5nm, 8nm, 11nm, 14nm, 17nm, 20nm, 23nm, 26nm, 29nm, 32nm, 35nm, 38nm, 41nm, 44nm, 47nm, 50nm, or a value within any two of the above ranges.

[0096] In some implementations, the thickness of the lithium cobalt oxide particles is controlled to be 0.1 μm. Within a 1μm range, the diffusion distance of lithium ions in the thickness direction can be effectively shortened, thereby improving ion migration efficiency. Simultaneously, it ensures sufficient structural stability and low ion transport impedance, thus enhancing the rate performance and cycle stability of the battery. If the sheet thickness of lithium cobalt oxide particles is less than 0.1μm, the structural stability of the particles decreases, making them prone to breakage during electrode fabrication or cycling, thereby compromising the integrity of the electrode structure and hindering the continuity of ion transport. If the sheet thickness of lithium cobalt oxide particles is greater than 1μm, it significantly prolongs the diffusion path of lithium ions in the thickness direction, increasing transport impedance and limiting the improvement of battery rate performance.

[0097] It should be noted that the sheet thickness of lithium cobalt oxide particles can be characterized using a combined ion beam cutting (CP) and scanning electron microscopy (SEM) method. The specific steps are as follows: After removing the film from the pouch cell, the multilayer cell is installed on the ion beam cutting instrument's sample stage, and the pre-section location is located under SEM. Ion beam cutting parameters are set, using a lower accelerating voltage (3-6 kV) to reduce the depth of the damaged layer. The ion beam current is adjusted in stages: first, a larger beam current (approximately 1 μA) is used for rapid coarse cutting; then, as the target interface area approaches, a smaller beam current (approximately 100 nA) is switched for fine polishing. The ion beam incident angle is controlled between 1° and 5° to obtain a smooth surface and a clear structure in the cross-section. After cutting and polishing, the sample position is kept unchanged, and the fresh cross-section is imaged and observed using the same scanning electron microscope. Multiple sheet-like lithium cobalt oxide particles with typical morphologies are identified and selected from the cross-sectional images, and their thickness dimensions are directly measured. Each particle is measured at least three times at different locations, and the measurements are recorded. Repeat the above steps to measure the thickness of at least 10 different lithium cobalt oxide particles. Finally, take the arithmetic mean of all valid measurements as the thickness of the lithium cobalt oxide particle.

[0098] For example, the thickness of the lithium cobalt oxide particles can be 0.10 μm, 0.16 μm, 0.22 μm, 0.28 μm, 0.34 μm, 0.40 μm, 0.46 μm, 0.52 μm, 0.58 μm, 0.64 μm, 0.70 μm, 0.76 μm, 0.82 μm, 0.88 μm, 0.94 μm, 1.00 μm, or a value within the range of any two of the above values.

[0099] In some implementations, by controlling the particle size Dv50 of lithium cobalt oxide particles to be between 0.1 μm and 20 μm, especially between 0.1 μm and 10 μm, the lithium cobalt oxide particles can form a suitable stacking structure and ion / electron conduction network in the electrode. This is beneficial for balancing high electrode compaction density with effective lithium-ion diffusion channels, thereby improving the battery's energy density, rate performance, and cycle stability. If the particle size Dv50 of lithium cobalt oxide particles is too small (<0.1 μm), the particles are prone to agglomeration and have an excessively large specific surface area, which may lead to increased side reactions, increased interfacial impedance, and affect the electrode's processing performance. If the particle size Dv50 of lithium cobalt oxide particles is too large (Dv50 > 20 μm), it will significantly prolong the solid-phase diffusion path of lithium ions inside the particles, limiting the battery's rapid charge and discharge capability, and may cause the lithium cobalt oxide particles to crack or fail during cycling due to local stress concentration.

[0100] It is understood that the particle size Dv50 of lithium cobalt oxide particles refers to the particle size corresponding to a cumulative volume distribution percentage of 50%, that is, the volume content of particles smaller than or equal to this size accounts for 50% of the total particle volume. The Dv50 test method can refer to standard GB / T19077-2016 / ISO 13320:2009, and is performed using a laser particle size analyzer (Malvern MasterSize 3000). For example, the particle size Dv50 of lithium cobalt oxide particles can be 0.1μm, 2.5μm, 5.0μm, 7.5μm, 10.0μm, 12.5μm, 15.0μm, 17.5μm, 20.0μm, or a value within any two of the above ranges.

[0101] In some embodiments, the X-ray diffraction pattern of the lithium cobalt oxide particles shows diffraction peaks at 2θ positions of 18.0°-18.9°, 37.4°-38°, 57.7°-58.3°, 36.6°-37.2°, 37.9°-38.5°, and 66.3°-66.9°, respectively. These peaks correspond to the characteristic diffraction peaks of the (002), (004), (006), (100), (101), and (110) crystal planes of the O2 phase structure. The appearance and position of these characteristic peaks are consistent with the standard card, indicating that the lithium cobalt oxide particles in this application possess an O2 phase hexagonal layered crystal structure. This structure has a wider lithium ion migration channel, which provides a key structural basis for the battery to maintain structural stability and achieve efficient ion transport under high voltage.

[0102] For example, see Figure 6 , Figure 6The image shows an X-ray diffraction pattern of lithium cobalt oxide particles in one embodiment of this application. As can be seen from the image, diffraction peaks exist at 2θ positions of 18.59°, 37.7°, 58°, 36.9°, 38.3°, and 66.6°, which correspond to the characteristic diffraction peaks of the (002), (004), (006), (100), (101), and (110) crystal planes of the O2 phase structure, respectively. The appearance and position of these characteristic peaks are consistent with the standard card, which indicates that the lithium cobalt oxide particles in this application have an O2 phase hexagonal layered crystal structure.

[0103] Furthermore, in some embodiments, 2θ is at 18.0° The diffraction peak corresponding to the (002) crystal plane in the range of 18.9° is denoted as I(002). This peak reflects the layered stacking characteristics of lithium cobalt oxide particles along the c-axis; 2θ at 66.3° The diffraction peak corresponding to the (110) crystal plane within the 66.9° range is denoted as I(110). This peak reflects the atomic arrangement of lithium cobalt oxide particles in the ab plane. This application controls the ratio of I(002) to I(110), I(002) / I(110), within 3... Within the range of 15, especially further control within 5 When the value is between 10 and 10, it indicates that the lithium cobalt oxide particles have a significant c-axis preferred orientation and a fully developed two-dimensional lamellar morphology, which helps lithium ions to be transported efficiently along the lamellar plane, thus providing a good crystallographic basis for improving the rate performance of the battery.

[0104] It should be noted that the diffraction peaks at 2θ positions of 18.3°-18.9°, 37.4°-38°, 57.7°-58.3°, 36.6°-37.2°, 37.9°-38.5°, and 66.3°-66.9° can be obtained by X-ray diffraction (XRD) testing according to the national standard GB / T 30904-2014. The specific testing method includes: grinding the sample and placing it on the sample stage of a Bruker D8 Advance X-ray diffractometer, using a Cu Kα radiation source (λ=1.5406 Å), setting the operating voltage to 40 kV and the current to 40 mA, and scanning at a rate of 2° / min at 10°... A scan was performed within a 75° (2θ) range with a scan step size of 0.02°. The resulting diffraction pattern was then compared with a standard PDF card of O2-phase lithium cobalt oxide using Jade software. The results showed that the characteristic diffraction peaks in the pattern perfectly matched the standard card, and no obvious impurity peaks were observed, indicating that lithium cobalt oxide has a pure O2 phase structure, thus confirming the aforementioned characteristic diffraction peaks. For example, the ratio of I(002) / I(110) can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a value within any range of the two values ​​listed above.

[0105] In some embodiments, the first oxide electrolyte and the second oxide electrolyte each independently comprise Li m Al n Ti q (PO4)3, Li7La3Zr2O 12 Or Li w La v At least one of TiO3, wherein 1.3≤m≤1.5, 0.3≤n≤0.5, 1.5≤q≤1.7, 0.3≤w≤0.5, and 0.9≤v≤1.0. This application, by employing the above-mentioned oxide electrolytes with rigid crystal frameworks, can provide structural support for O2 phase lithium cobalt oxide materials, effectively suppressing lattice distortion and harmful phase transitions during charging and discharging at high voltages; simultaneously, they also possess excellent electrochemical stability and high lithium-ion transport capacity, contributing to the construction of stable solid-state... Solidify the interface and reduce the risk of side reactions.

[0106] In some embodiments, controlling the particle size Dv50 of the first oxide electrolyte within the range of 50 nm to 1000 nm, especially when the particle size Dv50 is between 100 nm and 500 nm, facilitates the uniform dispersion of the oxide electrolyte in the solid electrolyte layer and the formation of a dense stacked structure. This improves the density and mechanical strength of the electrolyte layer, reduces porosity, and allows the oxide electrolyte to fully utilize its rigid framework structural advantages, providing stable mechanical support for the electrolyte layer and constructing a continuous and stable ion-mechanical coupling interface. Especially under low-temperature conditions, the dense oxide electrolyte structure can synergize with the high ionic conductivity of the halide electrolyte to reduce additional impedance caused by poor interfacial contact, thereby jointly improving the low-temperature cycling performance of the battery. If the particle size Dv50 of the oxide electrolyte is too small (<50 nm), it is prone to agglomeration, affecting the uniformity of dispersion; if the particle size Dv50 of the oxide electrolyte is >1000 nm, it will increase porosity, weakening the ion transport efficiency and mechanical strength of the electrolyte layer.

[0107] It is understood that the particle size Dv50 of oxide electrolytes refers to the particle size corresponding to a cumulative volume distribution percentage of 50%, that is, the volume content of particles smaller than or equal to this size accounts for 50% of the total particle volume. The Dv50 test method can refer to standard GB / T19077-2016 / ISO 13320:2009, and is performed using a laser particle size analyzer (Malvern MasterSize 3000). For example, the particle size Dv50 of oxide electrolytes can be 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, etc., or a value within any two of the above ranges.

[0108] In some embodiments, the first halide electrolyte and the second halide electrolyte each independently comprise Li3QCl6, where Q comprises at least one element selected from In, Y, Er, Ti, Al, Zr, and Ta. Because the ionic radius and electronegativity of element M are moderate, it is beneficial for forming and stabilizing a crystal framework with an anti-perovskite or similar topological structure. This framework can maintain a low lithium-ion migration barrier, thereby enabling the halide electrolyte to... It still maintains 10 under low temperature conditions such as 20℃ -4 -10 -3 Ionic conductivity on the order of S / cm. Furthermore, by selecting different M elements or their combinations, the lattice parameters and lithium-ion transport channel length can be controlled to a certain extent to match the layered structure and interfacial transport requirements of the positive electrode active material, thereby leveraging the high ion conductivity advantage of halide electrolytes over a wide temperature range, especially at low temperatures.

[0109] In some embodiments, controlling the particle size Dv50 of the first halide electrolyte within the range of 50 nm to 1500 nm, especially when the particle size Dv50 of the first halide electrolyte is within the range of 200 nm to 800 nm, facilitates a more uniform distribution and denser packing in the blended or stacked solid electrolyte layer, thereby improving the overall density of the electrolyte layer and reducing porosity. Especially under low-temperature conditions, smaller electrolyte particle size can reduce the detours of ion transport paths and the discontinuities of interfacial contacts, thereby better utilizing the high ionic conductivity characteristics of the halide electrolyte itself and further improving the low-temperature cycle performance of the battery. If the particle size Dv50 of the halide electrolyte is too small (<50 nm), the particles are prone to severe agglomeration, which is detrimental to uniform dispersion and interfacial construction; if the particle size Dv50 of the halide electrolyte is too large (>1500 nm), it will increase the voids and defects inside the electrolyte layer, weakening its structural density and ion transport efficiency.

[0110] It is understood that the particle size Dv50 of a halide electrolyte refers to the particle size corresponding to a cumulative volume distribution percentage of 50%, that is, the volume content of particles smaller than or equal to this size accounts for 50% of the total particle volume. The Dv50 test method can refer to standard GB / T19077-2016 / ISO 13320:2009, and is performed using a laser particle size analyzer (Malvern MasterSize 3000). For example, the particle size Dv50 of a halide electrolyte can be 50nm, 200nm, 350nm, 500nm, 650nm, 800nm, 950nm, 1100nm, 1250nm, 1400nm, 1500nm, etc., or a value within any two of the above ranges.

[0111] In some embodiments, the negative electrode includes a negative electrode active layer comprising lithium metal, wherein the areal capacity of the negative electrode active layer is controlled to be 4 mAh / cm². 2 -8mAh / cm 2 Within this range, the lithium metal anode possesses sufficient lithium-ion acceptance and storage capacity, enabling it to promptly and effectively absorb lithium ions released from O2-phase lithium cobalt oxide during high-voltage charging and discharging. This prevents excessive lithium-ion accumulation on the cathode surface and also helps suppress the precipitation reaction of lattice oxygen in the cathode material under high voltage, mitigating the risk of interlayer slippage and structural collapse caused by lithium-ion deintercalation. This provides crucial support for maintaining the stable layered structure of O2-phase lithium cobalt oxide, thereby improving the battery's cycle stability and volumetric energy density at high voltages. If the areal capacity of the anode active layer is less than 4 mAh / cm², [further improvements are needed]. 2 If the negative electrode has insufficient lithium-ion storage capacity, it will be difficult to effectively alleviate the structural stress of the positive electrode under high delithiation conditions, thus affecting the battery's capacity retention and cycle life. If the areal capacity of the negative electrode active layer is greater than 8 mAh / cm², the negative electrode will also be affected. 2 If the negative electrode active layer is too thick, it will not only prolong the lithium-ion transport path and increase the interface impedance, affecting the rate performance of the battery, but also reduce the volumetric energy density of the battery and may exacerbate the volume expansion effect and dendrite growth risk during cycling.

[0112] It should be noted that the specific testing method for the areal capacity of the negative electrode active layer includes: using a micrometer to measure the total thickness of the lithium-coated negative electrode sheet and the thickness of the blank current collector, taking 5 random measurements for each and averaging the results. The difference between the two measurements is the net thickness of the lithium metal layer (in cm). Then, according to the formula: Anode active layer areal capacity = Net lithium layer thickness × 2062, in mAh / cm². 2 The final areal capacity of the negative electrode active layer is calculated.

[0113] The present application will be further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application. Where specific experimental steps or conditions are not specified in the embodiments and comparative examples, they can be performed according to the conventional experimental steps or conditions described in the literature in the art. Reagents or instruments used, unless otherwise specified, are all commercially available conventional reagent products.

[0114] Example 1 This embodiment provides a method for preparing a battery, including the following steps: Step 1: Preparation of O2 phase lithium cobalt oxide 1) Preparation of O2 phase lithium cobalt oxide precursor. Sodium source Na2CO3 and cobalt source Co(OH)2 were weighed at a mass ratio of 1:2 and mixed in a ball mill at 400 rpm for 2 h to obtain a uniform mixture. The mixture was then calcined in air at 800℃ for 12 h to obtain P2 type Na2CO3 precursor. 0.7 (Co 0.8 M 0.2 O2 matrix, this matrix is ​​mixed with an excess of 5% LiNO3 / LiCl salt solution (molar ratio 1:1), and heat-treated at 280℃ for 6 h to achieve Na + With Li + After ion exchange, residual sodium and lithium salts were removed by washing with deionized water and dried to obtain the O2 phase LiCoO2 precursor with a particle size Dv50 of about 5 μm.

[0115] By adjusting the crystallization rate and ion exchange temperature during precursor synthesis, the lamellar morphology and structural parameters of the O2 phase LiCoO2 precursor can be effectively controlled. This can be achieved by appropriately increasing the crystallization rate and controlling the ion exchange temperature at 250°C. Within the 300℃ range, it is conducive to the formation of a sheet-like structure with a large ratio of major to minor diameter. The final O2 phase LiCoO2 product has an irregular polyhedral sheet-like morphology with a sheet thickness of about 0.5 μm, a minor diameter of about 2 μm, and a ratio of major to minor diameter of about 10.

[0116] 2) Preparation of O2 phase lithium cobalt oxide. 1 g of Li7La3Zr2O 12 The powder was dispersed in 3 L of a mixed solvent consisting of anhydrous ethanol (or other alcohol / deionized water) and a complexing agent (such as acetylacetone or citric acid) in a 1:1 volume ratio. The mixture was magnetically stirred at room temperature until a clear, stable, and transparent sol was formed. 10 g of the O2-phase LiCoO2 precursor powder prepared in step 1) was added to this sol to obtain a mixture. This mixture was then subjected to ultrasonic disruption for 20 minutes. For 30 minutes, allow the powder to disperse fully and evenly, avoiding agglomeration, to obtain a suspension. Then, transfer the suspension to a water bath and heat at 60°C. Gently heat at 80℃ with continuous stirring for 100-120 minutes to allow the solvent to evaporate slowly, gradually transforming the system into a viscous gel. Transfer the resulting gel to a vacuum drying oven and dry at 80℃. Dry at 120℃ for more than 12 hours to completely remove residual solvent, obtaining a dry powder coated with the amorphous precursor. Place the powder in a muffle furnace or tube furnace and dry it in a flowing oxygen or air atmosphere at 2... By heating to 500℃ at a rate of 5℃ / min and holding at that temperature for 4 h, Li7La3Zr2O can be obtained as a surface coating. 12 The O2 phase LiCoO2 coating layer has a thickness of approximately 25 nm. The thickness of the coating layer can be controlled by adjusting the concentration of the sol and the feed ratio of the cathode material to the sol. Generally, the higher the concentration and feed ratio, the thicker the coating layer.

[0117] Step 2: Preparation of the positive electrode sheet First, the O2 phase lithium cobalt oxide, conductive agent (Super P), and halide solid electrolyte (Li3YCl6) prepared in the first step were dry-mixed at a mass ratio of 90:5:5. Then, 3% of the total solid mass of polyvinylidene fluoride (PVDF) binder (dissolved in N) was added. The solvent was added to methylpyrrolidone and stirred at 2000 rpm for 30 minutes in a planetary centrifuge to form a uniform slurry with suitable viscosity. Then, an automatic coating machine was used to evenly coat the slurry onto a 12 μm thick aluminum foil current collector. Afterward, the coated electrode was transferred to a vacuum oven at 80°C and dried for 12 hours to completely remove the solvent. Finally, a roller press was used to cold-press the electrode at 200 MPa, ultimately controlling the thickness of the positive electrode active layer to approximately 100 μm and the compaction density to approximately 3.65 g / cm³. 3 Finally, the electrode is punched to a predetermined size (e.g., 4 cm × 5 cm) to obtain the positive electrode.

[0118] Step 3: Preparation of the negative electrode 1) Preparation of negative electrode current collector In an argon-protected glove box, a 20 μm thick lithium foil was composited with a copper current collector via a roll forming process to obtain an areal capacity of approximately 4.1 mAh / cm². 2 The negative electrode current collector. A tab structure is pre-reserved on the negative electrode current collector, with a width We2 of 10 mm, a length Le2 of 14 mm, and a thickness Te2 of 15 μm. The welding area between the external hard tab and the electrode tab is located in the area not covered by the electrolyte layer, and a 0.1-0.2Le2 empty foil area is reserved as the tab connection area.

[0119] 2) Preparation of solid electrolyte membranes First, oxide electrolyte or halide electrolyte and binder polyacrylic acid were mixed at a mass ratio of 98%:2% to prepare a slurry with a solid content of 37% using anhydrous heptane as solvent. Then, halide electrolyte slurry was first coated on the surface of polyethylene terephthalate (PET) film, with the wet film thickness controlled at 100 μm. After removing most of the solvent by gentle drying at 80°C, it was thoroughly dried under vacuum at 120°C. Next, oxide electrolyte slurry was coated on its surface with a wet film thickness of 80 μm, and the same drying process was performed. The total thickness of the resulting bilayer electrolyte film was approximately 180 μm.

[0120] 3) Preparation of negative electrode sheet The solid electrolyte membrane prepared in step 2) is cut to a size slightly larger than the negative electrode sheet. The negative electrode sheet is then sandwiched between two electrolyte membranes for preliminary encapsulation. The encapsulated assembly is then placed in a hot isostatic press and held at 60°C and 300±50 MPa for 5 minutes to complete the transfer of the electrolyte membrane to the negative electrode sheet. The resulting negative electrode sheet has a solid electrolyte covering structure in its tab region, with a length Ls2 of approximately 5.6 mm, a width Ws2 of approximately 5 mm, and a thickness Ts2 of approximately 180 μm. To verify the compactness of the transferred electrolyte layer, small samples can be cut, and their porosity can be tested using the mercury intrusion porosimetry method. It is typically confirmed that the porosity is less than or equal to 5%.

[0121] Step 4: Battery fabrication First, the cells are manually stacked according to a multi-layer stacking structure. The negative electrode sheet prepared in the third step is used as the core of the battery. Several layers of double-sided positive electrode sheets are alternately stacked on both sides, where the number of double-sided positive electrode sheets D satisfies: D=2X (X≥0, X is an integer). A single-sided negative electrode sheet is covered on the outermost side of the battery stacked structure (i.e., the outermost layer on the positive electrode side), thus forming a repeating unit of "positive electrode sheet / solid electrolyte layer / negative electrode sheet". The outermost layer is always a positive electrode sheet to form a symmetrical stacked structure to reduce edge effects. Then, a layer of high-temperature resistant polyimide tape is attached to the welding area of ​​the tab, so that it completely covers the welding point and extends to the periphery beyond the width of the tab. Finally, the stacked cells are placed in an aluminum-plastic packaging bag for vacuum sealing to obtain the battery.

[0122] Example 33 The difference between this embodiment and Embodiment 1 lies in the preparation of the solid electrolyte membrane in the negative electrode: The preparation of solid electrolyte membranes was carried out in a glove box or a high dew point drying room. First, the oxide electrolyte Li7La3Zr2O was prepared. 12The mixture was weighed and uniformly mixed with the halide electrolyte Li3YCl6 at a mass ratio of 45:55. Then, 2% (by weight of the total solids) of polyacrylic acid binder was added, and the solid content was adjusted to 37% using anhydrous heptane as a solvent to obtain a slurry. The slurry was then placed in a degassing machine at 1200 rpm for 30 minutes to remove air bubbles, resulting in a viscosity of approximately 3000. A uniform slurry of 5000 cP is prepared. Next, a polyimide (PI) or polyethylene terephthalate (PET) film with a smooth surface, slight elasticity, and good temperature resistance is selected as a temporary substrate. The slurry is uniformly coated onto the substrate using a doctor blade coater or a slot die coater, with the wet film thickness controlled at 25 μm. After coating, the film is first gently dried at 80°C to remove most of the solvent, and then transferred to a vacuum environment at 120°C for thorough drying. After drying, a solid electrolyte film is obtained attached to the temporary substrate, ready for subsequent transfer to the negative electrode sheet.

[0123] The rest of the content is the same as in Example 1.

[0124] The preparation methods of Examples 34-35 are basically the same as those of Example 33. The differences are shown in Tables 1-3.

[0125] The preparation methods of Examples 2-32 and Comparative Example 1 are basically the same as those of Example 1. The differences are shown in Tables 1-3.

[0126] Table 1

[0127] Table 2

[0128] Table 3

[0129] Test case 1. Ratio Performance Test At 25±1℃, charge the battery at a constant current of 0.1C to the cutoff voltage of 4.55V. After resting for a period of time (e.g., 5 minutes), discharge it at a constant current of 0.1C until the cutoff voltage of 3.0V. Record the discharge capacity and median voltage; this capacity can be used as the initial capacity. Gradually increase the charge and discharge rates to higher rates of 0.2C, 0.5C, 1C, 2C, and 5C, and finally return to the low rate of 0.1C. Record the discharge capacity at the low rate of 0.1C and compare it with the initial capacity. This ratio is the capacity retention rate after the rate test.

[0130] 2. Room temperature cycling performance test The battery was placed in a constant temperature room at 25±1℃ for 4 hours. It was then discharged at 1C to its lower limit voltage (3.0V), charged at 1.5C to its upper limit voltage (4.55V), and discharged again at 1C to its lower limit voltage (3.0V). This charge-discharge cycle constituted one test cycle. This cycle was repeated 800 times to calculate the battery's discharge capacity retention rate. The initial discharge capacity was Q1, and the discharge capacity after 800 cycles was Q2. Therefore, the discharge capacity retention rate was calculated as (Q2 / Q1)×100%.

[0131] 3. Low-temperature cycling performance test The battery was placed in a constant temperature room at -10±1℃ for 4 hours. It was then discharged at 1C to its lower limit voltage (3.0V), charged at 1.5C to its upper limit voltage (4.55V), and discharged at 1C to its lower limit voltage (3.0V). This charge-discharge cycle constituted one test cycle. This cycle was repeated 800 times to calculate the battery's discharge capacity retention rate. The initial discharge capacity was Q1, and the discharge capacity after 800 cycles was Q2. Therefore, the discharge capacity retention rate was calculated as (Q2 / Q1)×100%.

[0132] 4. Gram capacity test The lithium cobalt oxide particles to be tested were fabricated as the working electrode, and assembled into a coin cell with a lithium metal sheet (as the counter electrode and reference electrode) and an oxide electrolyte layer. An electrochemical workstation was used, with the charge / discharge rate set to 0.1C and the voltage window to 4.55V (vs. Li). + The half-cell (Li₂O₃) was cycled through charge and discharge, and the discharge capacity (in mAh) released during the discharge process was recorded. The formula for calculating the specific capacity is: Specific capacity (mAh / g) = Discharge capacity (mAh) / Mass of lithium cobalt oxide particles (g).

[0133] The test results are shown in Table 4.

[0134] Table 4

[0135] As can be seen from Tables 1-4, by selecting O2-phase lithium cobalt oxide with a specific chemical composition and combining it with an oxide / halide electrolyte layer that can partially cover the root of the tab, this application can effectively suppress the lattice distortion and phase transition of O2-phase lithium cobalt oxide under the working voltage while ensuring the high energy density of the battery. It can also provide sufficient lithium-ion migration channels, optimize the ion transport path, and improve the problems of burrs and lithium dendrites caused by stress concentration on the tab, thereby reducing the risk of internal short circuit. As a result, the battery has both excellent rate performance and cycle stability.

[0136] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A solid-state battery, comprising a positive electrode, a solid electrolyte layer, and a negative electrode stacked together, wherein, The positive electrode sheet includes a positive current collector, a positive active layer, and at least one positive tab. The positive active layer is disposed on at least one side surface of the positive current collector in the thickness direction. The positive tab extends out from the positive current collector, and the extension direction of the positive tab is perpendicular to the thickness direction of the positive current collector. The negative electrode sheet includes a negative electrode current collector, a negative electrode active layer, and at least one negative electrode tab. The negative electrode active layer is disposed on at least one side surface of the negative electrode current collector in the thickness direction. The negative electrode tab extends out from the negative electrode current collector, and the extension direction of the negative electrode tab is perpendicular to the thickness direction of the negative electrode current collector. Its features are, At least a portion of the positive electrode tab and / or the negative electrode tab is covered by the solid electrolyte layer, the solid electrolyte layer comprising at least one of a first oxide electrolyte and a first halide electrolyte; The positive electrode active layer includes a positive electrode active material, which includes lithium cobalt oxide particles. The lithium cobalt oxide particles have an O2 phase crystal structure and their general chemical formula is Li. x Na y Co k M z O2, M includes at least one element selected from Mg, Al, Ti, Zr, Ni, Mn, F, Y, Nb, La, B, and W, with 0.82≤x<1, 0.005≤y≤0.08, 0.8≤k≤1.05, and 0.005≤z≤0.

04.

2. The solid-state battery according to claim 1, characterized in that, The thickness direction of the negative electrode current collector is the first direction, the extension direction of the negative electrode tab is the second direction, and the third direction is perpendicular to both the first and second directions. Along the second direction, the length of the positive electrode tab is Le1, and the length of the solid electrolyte layer covering the positive electrode tab is Ls1, satisfying: 0.1Le1≤Ls1≤0.7Le1, preferably 0.3Le1≤Ls1≤0.6Le1; along the third direction, the length of the positive electrode tab is We1, and the length of the solid electrolyte layer covering the positive electrode tab is Ws1, satisfying: 0.1We1≤Ws1≤We1; And / or, along the second direction, the length of the negative electrode tab is Le2, and the length of the solid electrolyte layer covering the negative electrode tab is Ls2, satisfying: 0.1Le2≤Ls2≤0.7Le2, preferably 0.3Le2≤Ls2≤0.6Le2; along the third direction, the length of the negative electrode tab is We2, and the length of the solid electrolyte layer covering the negative electrode tab is Ws2, satisfying: 0.1We2≤Ws2≤We2.

3. The solid-state battery according to claim 2, characterized in that, Along the first direction, the length of the positive electrode tab is Te1, and the length of the solid electrolyte layer covering the positive electrode tab is Ts1, satisfying: 5Te1≤Ts1≤20Te1; And / or, along the first direction, the length of the negative electrode tab is Te2, and the length of the solid electrolyte layer covering the negative electrode tab is Ts2, satisfying: 5Te2≤Ts2≤20Te2; And / or, the area of ​​the positive electrode tab perpendicular to the first direction is S1, and the area of ​​the solid electrolyte layer covering the positive electrode tab is S2, satisfying: 0.03≤S2 / S1≤0.6; And / or, the area of ​​the negative electrode tab perpendicular to the first direction is S3, and the area of ​​the solid electrolyte layer covering the negative electrode tab is S4, satisfying: 0.03≤S4 / S3≤0.

6.

4. The solid-state battery according to claim 1, characterized in that, The porosity of the solid electrolyte layer is less than or equal to 5%; And / or, the thickness of the solid electrolyte layer is 10μm-500μm, preferably 100μm-500μm.

5. The solid-state battery according to claim 1, characterized in that, The solid electrolyte layer comprises a blend of the first oxide electrolyte and the first halide electrolyte, wherein, based on the mass of the solid electrolyte layer, the mass content of the first oxide electrolyte is 40%-50%, and the mass content of the first halide electrolyte is 50%-60%; or... The solid electrolyte layer includes a first electrolyte layer and a second electrolyte layer stacked together. The first electrolyte layer is close to the negative electrode and has a thickness of 5μm-150μm. The second electrolyte layer is close to the positive electrode and has a thickness of 5μm-350μm. Preferably, the first electrolyte layer comprises the first oxide electrolyte, and the second electrolyte layer comprises the first halide electrolyte; or, the first electrolyte layer comprises a sulfide electrolyte, and the second electrolyte layer comprises at least one of the first oxide electrolyte and the first halide electrolyte.

6. The solid-state battery according to claim 1, characterized in that, The lithium cobalt oxide particles are in the form of sheets, with a plane perpendicular to their thickness direction as the projection surface. The orthographic projection of the lithium cobalt oxide particles on the projection surface has a minor diameter A μm. The direction of the line connecting the two points furthest apart in the outer contour of the orthographic projection is the fourth direction, and the direction perpendicular to the fourth direction is the fifth direction. The minor diameter A μm is the length of the orthographic projection along the fifth direction and perpendicularly bisects the fourth direction, satisfying: 1≤A≤10. Preferably, the orthographic projection of the lithium cobalt oxide particle on the projection surface also has a major diameter B μm, wherein the major diameter B μm is the length of the orthographic projection along the fourth direction, satisfying: 5≤B / A≤40.

7. The solid-state battery according to claim 6, characterized in that, At least a portion of the surface of the lithium cobalt oxide particles has a coating layer with a thickness of 5 nm to 50 nm, and the coating layer includes at least one of a second oxide electrolyte and a second halide electrolyte. And / or, the thickness of the lithium cobalt oxide particles is 0.1 μm-1 μm; And / or, the particle size Dv50 of the lithium cobalt oxide particles is 0.1μm-20μm, preferably 0.1μm-10μm.

8. The solid-state battery according to claim 1, 6, or 7, characterized in that, The X-ray diffraction pattern of the lithium cobalt oxide particles shows diffraction peaks at 2θ values ​​of 18.0°-18.9°, 37.4°-38°, 57.7°-58.3°, 36.6°-37.2°, 37.9°-38.5°, and 66.3°-66.9°. Preferably, 2θ belongs to the diffraction peak of the (002) crystal plane in the range of 18.0°-18.9°, and the intensity of the diffraction peak of the (002) crystal plane is I(002). 2θ belongs to the diffraction peak of the (110) crystal plane in the range of 66.3°-66.9°, and the intensity of the diffraction peak of the (110) crystal plane is I(110). The following conditions are met: 3≤I(002) / I(110)≤15, preferably 5≤I(002) / I(110)≤10.

9. The solid-state battery according to claim 1, 5, or 7, characterized in that, The first oxide electrolyte and the second oxide electrolyte each independently comprise Li m Al n Ti q (PO4)3, Li7La3Zr2O 12 Li w La v At least one of TiO3, wherein 1.3≤m≤1.5, 0.3≤n≤0.5, 1.5≤q≤1.7, 0.3≤w≤0.5, and 0.9≤v≤1.0; And / or, the particle size Dv50 of the first oxide electrolyte is 50nm-1000nm, preferably 100nm-500nm; And / or, the first halide electrolyte and the second halide electrolyte each independently comprise Li3QCl6, where Q comprises at least one element selected from In, Y, Er, Ti, Al, Zr, and Ta; And / or, the particle size Dv50 of the first halide electrolyte is 50nm-1500nm, preferably 200nm-800nm; And / or, the general chemical formula of the sulfide electrolyte is Li b A e T d Z c X a , 1≤a≤1.5, 5.5≤b≤7, 0≤c≤1, 3.5≤d≤5, 0≤e≤1, A includes at least one of P, As, and Sb, T includes at least one of Si and Ge, Z includes at least one of O and Se, and X includes at least one of Cl, Br, and I.

10. The solid-state battery according to claim 1, characterized in that, The negative electrode includes a negative electrode active layer, which comprises lithium metal, and the areal capacity of the negative electrode active layer is 4 mAh / cm². 2 -8mAh / cm 2 .

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