A lithium supplement, a positive electrode material, a solid-state secondary battery, and an electric device

Abstract

The application discloses a lithium supplement, a positive electrode material, a solid-state secondary battery and an electric device, and relates to the technical field of batteries. 2‑2x M x S 1‑y‑z Se y Te z , wherein M is a transition metal element, 0<=x<=0.5, 0<=y<=0.5, 0<=z<=0.5, and x+y+z>0; and the chemical formula B is Li2S / MS n , wherein M is a transition metal element, MS n is a transition metal sulfide, and 1<=n<=2. By introducing the transition metal M into the Li2S crystal lattice, the Li-S bond energy is weakened, the delithiation overpotential is significantly reduced, the lithium supplement can quickly release lithium ions in a voltage window of 2.0-4.3 V, and the electrochemical activity is much higher than that of pure Li2S. Meanwhile, the main framework of the lithium supplement is still a sulfide, which has natural chemical compatibility with a sulfide solid-state electrolyte, avoids the generation of high-impedance byproducts at the interface, and improves the long-term stability of the interface.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a lithium replenishing agent, a cathode material, a solid-state secondary battery, and an electrical device. Background Technology

[0002] Sulfide-based all-solid-state batteries represent a crucial direction for next-generation high-energy-density batteries. To achieve ultra-high energy densities exceeding 500 Wh / kg, anodes are evolving towards electrodeless designs (where active lithium is entirely provided by the cathode) and high-silicon anodes (where silicon content in silicon-carbon materials exceeds 30%). However, both of these anode systems face a severe problem of "active lithium consumption": electrodeless batteries consume a large amount of lithium during the initial charge-discharge cycle to form an SEI film, while high-silicon anodes typically exhibit low initial coulombic efficiency.

[0003] Conventional lithium replenishment agents have several drawbacks in sulfide all-solid-state batteries, such as high Li2S decomposition potential (about 2.8V), low ionic / electronic conductivity, poor delithiation kinetics in the all-solid-state system, limited lithium replenishment effect, chemical incompatibility with sulfide solid electrolytes, and easy generation of high-resistivity byproducts at the interface, leading to a decline in cycle performance. Summary of the Invention

[0004] This application provides a lithium replenishing agent, a cathode material, a solid-state secondary battery, and an electrical device, aiming to improve the problems of existing lithium replenishing agents in sulfide all-solid-state batteries, such as low ionic / electronic conductivity, poor delithiation kinetics in all-solid-state systems, limited lithium replenishment effect, chemical incompatibility with sulfide solid electrolytes, easy formation of high-resistivity byproducts at the interface, and decreased cycle performance.

[0005] In a first aspect, this application provides a lithium replenishing agent for use in the positive electrode of a sulfide all-solid-state battery, comprising at least one of compounds having chemical formula A and chemical formula B, wherein: Chemical formula A is: Li 2-2x M x S 1-y-z Se y Te z M is a transition metal element, 0≤x≤0.5, 0≤y≤0.5, 0≤z≤0.5, x+y+z>0; Chemical formula B is: Li₂S / MS n M is a transition metal element, and MS n It is a transition metal sulfide, 1≤n≤2.

[0006] This application introduces the transition metal M into the Li₂S lattice, weakening the Li-S bond energy and significantly reducing the delithiation overpotential. The lithium replenishment agent can rapidly release lithium ions within a voltage window of 2.0-4.3V, exhibiting electrochemical activity far exceeding that of pure Li₂S. Simultaneously, the main framework of the lithium replenishment agent remains a sulfide, possessing natural chemical compatibility with sulfide solid electrolytes (such as Li₆PS₅Cl), avoiding the formation of high-resistivity byproducts at the interface and improving long-term interfacial stability. The introduction of Se and / or Te elements utilizes the characteristics of group-dependent elements to optimize the lithium replenishment agent's performance. Se doping improves the ionic conductivity of the material, while Te doping significantly enhances the electronic conductivity. Their synergistic effect further reduces the delithiation overpotential of the lithium replenishment agent, improving lithium replenishment efficiency. Furthermore, the introduction of Se and Te does not alter the material's compatibility with the sulfide electrolyte, maintaining interfacial stability.

[0007] In some embodiments, the transition metal element includes at least one selected from Ni, Co, Fe, Mn, Cu, Zn, Mo, W, V, and Cr. These transition metal elements can weaken the Li-S bond energy, significantly reducing the delithiation overpotential. The lithium replenishing agent can rapidly release lithium ions within a voltage window of 2.0-4.3V, exhibiting electrochemical activity far exceeding that of pure Li₂S.

[0008] In some embodiments, the lithium replenishing agent has a particle size of 0.3 μm to 1.5 μm. The elemental composition and density of the lithium replenishing agent are similar to those of the sulfide electrolyte. After elemental doping, the density of the lithium replenishing agent falls between that of the electrolyte and the cathode material. The particle size range of the lithium replenishing agent is a comprehensive consideration of the particle sizes of both the cathode and electrolyte. Within this range, the lithium replenishing agent can be uniformly dispersed in the electrode slurry, avoiding insufficient reaction and inadequate lithium replenishment due to excessively large particle sizes. It also prevents agglomeration and increased surface side reactions caused by excessively small particle sizes. Furthermore, this particle size range facilitates close contact between the lithium replenishing agent and the electrode active material, enabling stable and efficient lithium-ion release during charge and discharge, thereby improving the battery's initial coulombic efficiency and cycle life. In addition, this particle size range also considers the feasibility of the preparation process, reducing grinding or grading costs and facilitating industrial production.

[0009] In some embodiments, at least a portion of the surface of the lithium supplement has a coating layer, the coating material comprising at least one of carbon, a conductive polymer, and a sulfide electrolyte. The coating material comprising at least one of carbon, a conductive polymer, and a sulfide electrolyte can enhance electron / ion transport capabilities and suppress side reactions.

[0010] Secondly, this application provides a positive electrode material, including a positive electrode active material, a sulfide solid electrolyte, a conductive agent, a binder, and the lithium supplement agent described in the first aspect.

[0011] In some embodiments, the lithium replenishing agent accounts for 0.5% to 3% of the mass of the cathode material. Within this range, the lithium replenishing agent can effectively compensate for irreversible lithium loss during the first charge, significantly improve the battery's initial coulombic efficiency and reversible capacity, improve the cell's cycle stability, and avoid problems such as a decrease in the proportion of positive electrode active material, electrode coating cracking, or increased resistance caused by excessive lithium replenishing agent. It also helps maintain good mechanical strength and conductive network of the positive electrode sheet and suppresses the adverse effects of lithium replenishing agent decomposition residues on the electrolyte and electrode interface.

[0012] Thirdly, this application provides a solid-state secondary battery, including a positive electrode, a sulfide solid electrolyte layer and a negative electrode, wherein the positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector, and the positive electrode material layer includes the positive electrode material described in the second aspect.

[0013] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one side of the negative current collector, wherein the negative electrode material layer includes at least one of silicon-carbon composite materials or at least one of conductive carbon materials. High-energy-density negative electrode-less or silicon-carbon negative electrode systems suffer severe loss of active lithium during the first charge-discharge cycle. Existing lithium replenishing agents either undergo harmful side reactions with sulfide electrolytes (such as LFO, LNO) or have low electrochemical activity (such as Li2S). However, by selecting the lithium replenishing material of this application, only the positive electrode needs to provide the lithium replenishing agent, which can effectively compensate for the low first-cycle efficiency loss of the silicon-carbon negative electrode. Simultaneously, the transition metal sulfides in the delithiation products possess a certain degree of mechanical flexibility, which helps alleviate the interfacial stress caused by the volume expansion of the silicon negative electrode, further improving cycle stability. The lithium replenishing agent in this application has a high theoretical lithium replenishment capacity (close to or exceeding 1000 mAh / g), which can provide sufficient active lithium source for the anode-free system, improve the problem of short lifespan caused by lithium source depletion in the anode-free system, and provide key technical support for achieving ultra-high energy density batteries of >500 Wh / kg.

[0014] In some embodiments, the silicon-carbon composite material contains silicon by mass of 30% or more. A silicon mass percentage of 30% or more can significantly improve the specific capacity of the negative electrode (>1500 mAh / g vs. graphite, which has a specific capacity of 340 mAh / g), drastically reducing the amount of negative electrode material used and the thickness of the negative electrode sheet. This allows for better matching with a high-capacity positive electrode, achieving a leap in the overall energy density of the battery; or... The conductive carbon material includes at least one of carbon nanotubes, carbon fibers, and hard carbon. These conductive carbon materials can serve as a three-dimensional conductive framework in an anode-free system, providing uniform nucleation sites for lithium deposition, effectively reducing local current density, and suppressing lithium dendrite growth. Carbon nanotubes and carbon fibers, with their one-dimensional high aspect ratio structure, can construct a continuous and flexible conductive network, maintaining electron contact even under large volume changes. Hard carbon possesses abundant nanopores and defect sites, enabling reversible storage of lithium ions or serving as a host for lithium deposition, thereby improving the coulombic efficiency of lithium deposition / stripping. Using these conductive carbon materials to replace traditional metallic lithium anodes avoids the use of excessive lithium and works synergistically with the lithium replenishment agent of this application: the lithium replenishment agent provides initial active lithium, and the conductive carbon material, as a framework, guides uniform lithium deposition, thereby significantly extending the cycle life of the anode-free battery.

[0015] Fourthly, this application provides an electrical device including the solid-state secondary battery described in the third aspect. Attached Figure Description

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

[0017] Figure 1 This is an XRD pattern of a lithium supplement agent according to an embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Sulfide-based all-solid-state batteries represent a crucial direction for next-generation high-energy-density batteries. To achieve ultra-high energy densities exceeding 500 Wh / kg, anodes are evolving towards electrodeless designs (where active lithium is entirely provided by the cathode) and high-silicon anodes (where silicon content in silicon-carbon materials exceeds 30%). However, both of these anode systems face a severe problem of "active lithium consumption": electrodeless batteries consume a large amount of lithium during the initial charge-discharge cycle to form an SEI film, while high-silicon anodes typically exhibit low initial coulombic efficiency.

[0020] Conventional lithium replenishment agents have several drawbacks in sulfide all-solid-state batteries, such as high Li2S decomposition potential (about 2.8V), low ionic / electronic conductivity, poor delithiation kinetics in the all-solid-state system, limited lithium replenishment effect, chemical incompatibility with sulfide solid electrolytes, and easy generation of high-resistivity byproducts at the interface, leading to a decline in cycle performance.

[0021] For example, a lithium replenishing agent used in the positive electrode of a lithium-ion battery is a lithium sulfide (Li). x S, where 1 / 3 ≤ x ≤ 2), specifically can be Li₂S, Li₂S₂, Li₂S₄, or Li₂S₆. This lithium replenisher releases lithium ions during the first charge, compensating for the irreversible capacity loss caused by SEI film formation, thereby improving the initial coulombic efficiency and battery energy density. Its delithiation byproduct S x 2- The shuttle effect can be avoided by adsorption confinement through conductive agents (such as porous carbon, graphene, etc.). It is mainly used in liquid lithium-ion battery systems. However, when directly applied to sulfide all-solid-state batteries, the following drawbacks exist: insufficient electrochemical activity: Li₂S has a high decomposition potential (approximately 2.8 V vs. Li₂). + Within the typical operating voltage window (2.5-4.3V) of sulfide-based all-solid-state batteries, Li₂S struggles to rapidly release sufficient lithium ions during the initial charging phase, significantly reducing its lithium replenishment efficiency. Poor lithium removal kinetics: Li₂S itself has low ionic and electronic conductivity. In an all-solid-state system, the lack of liquid electrolyte wetting severely limits the lithium removal reaction kinetics, making efficient lithium replenishment difficult. Lack of compatibility with sulfide systems: Existing technologies only consider liquid systems and do not account for the interfacial compatibility between sulfide solid electrolytes and lithium replenishing agents. In practical applications, this may lead to failure due to poor interfacial contact.

[0022] For example, in sulfide all-solid-state batteries, an oxide lithium replenisher is used, with a lithium replenishment layer containing Li5FeO4 (LFO) or LiNiO2 (LNO) on the positive electrode side, or Li5FeO4 is coated on the surface of the nickel-rich positive electrode to achieve lithium replenishment and improve interface stability. However, the above-mentioned lithium replenishers undergo interfacial side reactions with the sulfide electrolyte: the oxide lithium replenisher (LFO, LNO) is chemically incompatible with the sulfide solid electrolyte (such as Li6PS5Cl). During positive electrode preparation or battery cycling, a chemical reaction occurs at the interface between the two, generating high-resistivity phosphate, sulfate, or oxysulfide impurities, leading to a sharp increase in interfacial impedance, increased battery polarization, and a significant decrease in cycle life. The lithium replenisher itself is structurally unstable: after delithiation, the oxide lithium replenisher is often accompanied by the release of lattice oxygen, which further reacts with the sulfide electrolyte, exacerbating interface degradation and severely limiting its application in sulfide all-solid-state batteries.

[0023] There is an urgent need to develop a new lithium replenishing agent suitable for solid-state batteries that has both high lithium replenishing activity and long-term compatibility with sulfide electrolytes.

[0024] In view of this, this application provides a lithium replenishing agent, a cathode material, a solid-state secondary battery, and an electrical device, aiming to improve the problems of existing lithium replenishing agents in sulfide all-solid-state batteries, such as low ionic / electronic conductivity, poor delithiation kinetics in all-solid-state systems, limited lithium replenishment effect, chemical incompatibility with sulfide solid electrolytes, easy generation of high-resistivity byproducts at the interface, and decreased cycle performance.

[0025] In a first aspect, this application provides a lithium replenishing agent for use in the positive electrode of a sulfide all-solid-state battery, comprising at least one of compounds having chemical formula A and chemical formula B, wherein: Chemical formula A is: Li 2-2x M x S 1-y-z Se y Te z M is a transition metal element, 0≤x≤0.5, 0≤y≤0.5, 0≤z≤0.5, x+y+z>0; Chemical formula B is: Li₂S / MS n M is a transition metal element, and MS n It is a transition metal sulfide, 1≤n≤2.

[0026] This application introduces the transition metal M into the Li₂S lattice, weakening the Li-S bond energy and significantly reducing the delithiation overpotential. The lithium replenishment agent can rapidly release lithium ions within a voltage window of 2.0-4.3V, exhibiting electrochemical activity far exceeding that of pure Li₂S. Simultaneously, the main framework of the lithium replenishment agent remains a sulfide, possessing natural chemical compatibility with sulfide solid electrolytes (such as Li₆PS₅Cl), avoiding the formation of high-resistivity byproducts at the interface and improving long-term interfacial stability. The introduction of Se and / or Te elements utilizes the characteristics of group-dependent elements to optimize the lithium replenishment agent's performance. Se doping improves the ionic conductivity of the material, while Te doping significantly enhances the electronic conductivity. Their synergistic effect further reduces the delithiation overpotential of the lithium replenishment agent, improving lithium replenishment efficiency. Furthermore, the introduction of Se and Te does not alter the material's compatibility with the sulfide electrolyte, maintaining interfacial stability.

[0027] In conjunction with the first aspect, in some embodiments provided in this application, the transition metal element includes at least one selected from Ni, Co, Fe, Mn, Cu, Zn, Mo, W, V, and Cr. These transition metal elements can weaken the Li-S bond energy, significantly reducing the delithiation overpotential. The lithium replenishing agent can rapidly release lithium ions within a voltage window of 2.0-4.3V, exhibiting electrochemical activity far exceeding that of pure Li₂S.

[0028] In conjunction with the first aspect, in some embodiments provided in this application, the particle size of the lithium replenishing agent is 0.3 μm to 1.5 μm. The elemental composition and density of the lithium replenishing agent are similar to those of the sulfide electrolyte. After elemental doping, the density of the lithium replenishing agent is between that of the electrolyte and the cathode material. The particle size range of the lithium replenishing agent is a comprehensive consideration of the particle sizes of the cathode and electrolyte. Within this range, the lithium replenishing agent can be uniformly dispersed in the electrode slurry, avoiding insufficient reaction and inadequate lithium replenishment due to excessively large particle sizes, while preventing agglomeration and increased surface side reactions caused by excessively small particle sizes. This facilitates close contact between the lithium replenishing agent and the electrode active material, achieving stable and efficient lithium-ion release during charge and discharge, thereby improving the battery's initial coulombic efficiency and cycle life. Furthermore, this particle size range also considers the feasibility of the preparation process, reducing grinding or grading costs and facilitating industrial production. In some embodiments, the lithium replenishing agent is not limited to nanoparticles but can also be prepared into nanowires, nanosheets, or other morphologies.

[0029] In conjunction with the first aspect, in some embodiments provided in this application, at least a portion of the surface of the lithium replenishing agent has a coating layer, the coating layer material including at least one of carbon, a conductive polymer, and a sulfide electrolyte. The coating layer material including at least one of carbon, a conductive polymer, and a sulfide electrolyte can enhance electron / ion transport capabilities and suppress side reactions. The conductive polymer can be polypyrrole, polyaniline, etc. The sulfide electrolyte can be Li2S-ZrS2, Li3PS4, etc.

[0030] Secondly, this application provides a positive electrode material, including a positive electrode active material, a sulfide solid electrolyte, a conductive agent, a binder, and the lithium supplement agent described in the first aspect.

[0031] In conjunction with the second aspect, in some embodiments provided in this application, the mass percentage of the lithium replenishing agent in the cathode material is 0.5% to 3%. Within this range, the lithium replenishing agent can effectively compensate for irreversible lithium loss during the first charge, significantly improve the battery's initial coulombic efficiency and reversible capacity, while also improving the cell's cycle stability. Furthermore, it avoids problems such as a decrease in the proportion of positive electrode active material, electrode coating cracking, or increased resistance caused by excessive lithium replenishing agent. This also helps maintain good mechanical strength and conductive network of the positive electrode sheet, and suppresses the adverse effects of lithium replenishing agent decomposition residues on the electrolyte and electrode interface. A further preferred range of 0.5-2 wt% achieves a better balance between lithium replenishment effect, energy density, and cycle stability, while reducing cost and making it suitable for large-scale applications.

[0032] It should be noted that, in addition to being directly mixed into the cathode material, lithium replenishing agents can also be made into an independent lithium replenishing layer, coated between the cathode layer and the solid electrolyte layer, or pre-composite with conductive agents and then added to other cathode materials.

[0033] Thirdly, this application provides a solid-state secondary battery, including a positive electrode, a sulfide solid electrolyte layer and a negative electrode, wherein the positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector, and the positive electrode material layer includes the positive electrode material described in the second aspect.

[0034] In conjunction with the third aspect, in some embodiments provided in this application, the negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one side of the negative current collector, wherein the negative electrode material layer includes at least one of silicon-carbon composite materials, or at least one of conductive carbon materials. High-energy-density negative electrode-less or silicon-carbon negative electrode systems suffer severe loss of active lithium during the first charge-discharge cycle. Existing lithium replenishing agents either undergo harmful side reactions with sulfide electrolytes (such as LFO, LNO) or have low electrochemical activity (such as Li2S). However, by selecting the lithium replenishing material of this application, only the positive electrode needs to provide the lithium replenishing agent, which can effectively compensate for the low first-cycle efficiency loss of the silicon-carbon negative electrode. Simultaneously, the transition metal sulfides in the delithiation products possess a certain degree of mechanical flexibility, which helps alleviate the interfacial stress caused by the volume expansion of the silicon negative electrode, further improving cycle stability. The lithium replenishing agent in this application has a high theoretical lithium replenishment capacity (close to or exceeding 1000 mAh / g), which can provide sufficient active lithium source for the anode-free system, improve the problem of short lifespan caused by lithium source depletion in the anode-free system, and provide key technical support for achieving ultra-high energy density batteries of >500 Wh / kg.

[0035] It should be noted that a negative electrode-free system refers to a system where no negative electrode active material layer (such as graphite, silicon-carbon, or lithium metal foil) is pre-placed on the negative electrode side. Instead, a conductive carbon material layer (such as carbon nanotubes, carbon fibers, hard carbon, etc.) is directly or indirectly coated onto the negative electrode current collector (e.g., copper foil). During the first charge of the battery, lithium ions in the positive electrode migrate to the negative electrode and are deposited as metallic lithium on the surface of the current collector or conductive carbon framework, forming an in-situ grown metallic lithium negative electrode. The most significant characteristic of this system is that all active lithium comes from the lithium-rich positive electrode material on the positive electrode side. Therefore, the capacity and efficiency of the positive electrode active material directly determine the total capacity and cycle life of the battery. A negative electrode-free design can significantly improve energy density (eliminating the volume and mass of the negative electrode active material), but the presence of interfacial side reactions leads to challenges such as rapid lithium source depletion, lithium dendrite growth, and low coulombic efficiency. The high theoretical capacity of the lithium replenishment agent in this application and its good compatibility with sulfide electrolytes provide an effective solution to the lithium source shortage problem in negative electrode-free systems, thereby significantly improving the cycle life of high-energy cell systems without negative electrodes.

[0036] In conjunction with the third aspect, in some embodiments provided in this application, the silicon-carbon composite material has a silicon mass percentage greater than or equal to 30%. A silicon mass percentage greater than or equal to 30% can significantly improve the specific capacity of the negative electrode (>1500mAh / g vs. graphite specific capacity is 340mAh / g), greatly reduce the amount of negative electrode material used and the thickness of the negative electrode sheet, thereby matching with the high-capacity positive electrode and achieving a leap in the overall energy density of the battery.

[0037] In conjunction with the third aspect, in some embodiments provided in this application, the conductive carbon material includes at least one of carbon nanotubes, carbon fibers, and hard carbon. The aforementioned conductive carbon material can serve as a three-dimensional conductive framework in an anode-free system, providing uniform nucleation sites for lithium deposition, effectively reducing local current density, and suppressing lithium dendrite growth. Carbon nanotubes and carbon fibers, with their one-dimensional high aspect ratio structure, can construct continuous and flexible conductive networks, maintaining electronic contact even under large volume changes. Hard carbon has abundant nanopores and defect sites, enabling reversible storage of lithium ions or serving as a host for lithium deposition, thereby improving the coulombic efficiency of lithium deposition / stripping. Using the aforementioned conductive carbon material to replace the traditional metallic lithium anode avoids the use of excessive lithium and works synergistically with the lithium replenishment agent of this application: the lithium replenishment agent provides initial active lithium, and the conductive carbon material, as a framework, guides uniform lithium deposition, thereby significantly extending the cycle life of the anode-free battery.

[0038] Fourthly, this application provides an electrical device including the solid-state secondary battery described in the third aspect.

[0039] The present application will be further described below with reference to specific embodiments.

[0040] Example 1 Lithium supplement preparation: In an argon glove box, Li₂S and NiS were mixed at a molar ratio of 0.8:0.2, ball-milled for 15 hours, then heat-treated at 500℃ for 4 hours, cooled and ground to obtain a particle size of Dv. 50 Li is 1.0 μm 1.6 Ni 0.2 S powder, prepared Li 1.6 Ni 0.2 S powder was analyzed by X-ray diffraction (XRD, Cu Kα radiation), such as Figure 1 As shown, its diffraction pattern is basically consistent with the standard pattern of undoped Li2S, indicating that the doping of Ni element did not change the antifluorite main crystal structure of Li2S. No diffraction peaks belonging to NiS or other nickel-containing impurities were observed in the entire XRD pattern, proving that the obtained product is a single pure phase.

[0041] Example 2 Preparation of lithium supplement: Li₂S and Li₂Se were mixed in a molar ratio of 1:1, ball-milled at high energy for 12 hours, and heat-treated at 500℃ for 4 hours to obtain a particle size of Dv. 50 Li₂S with a thickness of 1.2 μm 0.5 Se 0.5 .

[0042] Example 3 Preparation of lithium supplement: Li₂S, NiS, and Li₂Se were mixed in a molar ratio of 0.4:0.1:0.5, ball-milled for 18 hours, and heat-treated at 550℃ for 4 hours to obtain a particle size of Dv. 50 Li with a thickness of 0.8 μm 1.8 Ni 0.1 S 0.5 Se 0.5 .

[0043] Example 4 Preparation of lithium supplement: Lithium metal and CoS2 were mixed at a 2:1 molar ratio using a lithiumthermal reduction method and reacted at 400℃ for 4 hours. At least a portion of the surface of the lithium supplement had a coating layer. The coating material was a sulfide electrolyte Li5.5PS4.5Cl1.5 (Dv). 50 The electrolyte and sintered Li₂S / CoS₂ were combined by ball milling at a mass ratio of 0.08:1 for 5 hours at 400 rpm. After sintering, a particle size of Dv was obtained. 50 It is a 1.5 μm Li2S / CoS2 nanocomposite material.

[0044] Example 5 Lithium supplement preparation: Li₂S, Li₂Se, and Li₂Te were mixed in a molar ratio of 0.8:0.1:0.1, ball-milled for 24 hours, and heat-treated at 550℃ for 6 hours. At least part of the surface of the lithium supplement had a coating layer, the coating material being carbon raw material acetylene black. The acetylene black was then mixed with the sintered Li₂S... 0.8 Se 0.1 Te 0.1 The composite material was ball-milled at a mass ratio of 0.05:1 at 300 rpm for 6 hours. After sintering, a particle size of Dv was obtained. 50 Li₂S with a thickness of 0.3 μm 0.8 Se 0.1 Te 0.1 .

[0045] Example 6 Preparation of lithium supplement: Li₂S and NiS were mixed in a 1:1 molar ratio, ball-milled for 15 hours, and heat-treated at 550℃ for 6 hours. At least part of the surface of the lithium supplement had a coating layer made of conductive polymer polyaniline. LiNi was added to an acetone solution containing aniline monomers. 0.5S, while continuously stirring, add an appropriate amount of oxidant to induce oxidative polymerization of aniline monomers in LiNi. 0.5 A coating layer is formed on the S surface, with polyaniline and LiNi 0.5 With a mass ratio of S of 0.02:1, a particle size of Dv was obtained. 50 LiNi with a thickness of 1.3 μm 0.5 S.

[0046] Comparative Example 1 It is a lithium supplement for pure Li2S.

[0047] Performance testing The lithium supplementer of Examples 1 to 6 and Comparative Example 1 was combined with the positive electrode active material (NCM811) and the sulfide solid electrolyte (Li6PS5Cl, Dv). 50 The cathode composite powder was obtained by mixing a lithium-ion polymer (0.5μm~1.2μm) and a conductive agent (VGCF) at a ratio of 2:70:25:3 in an argon glove box and then ball-milling the mixture at 200 rpm in a high-energy ball mill. The cathode powder without lithium supplementation agent was used as the control group powder.

[0048] Silicon-carbon composite material (silicon content > 40 wt%, specific capacity > 2000 mAh / g), sulfide electrolyte (Li6PS5Cl, Dv) 50 The first negative electrode composite powder was obtained by mixing VGCF (0.5-1.2μm) and VGCF at a ratio of 70:25:5 and then ball milling it at 200 rpm for 1 hour in a high-energy ball mill.

[0049] No negative electrode: A layer with a loading of 3 mg / cm² is coated on the surface of the copper foil. 2 Carbon fiber VGCF conductive coating, VGCF specific surface area less than 20m² 2 / g, accounting for >97% of the mass in the coating, forming the second negative electrode.

[0050] 3mg / cm² 2 The carbon fiber VGCF conductive coating is coated on the surface of the PET film and then dried. After drying, it is transferred to the surface of the LiCu composite tape (Cu foil thickness 6μm, with a lithium metal layer of thickness 20μm) near the lithium metal side by a hot roller press to obtain the third negative electrode sheet for lithium replenishment.

[0051] Solid-state battery assembly: Weigh 100mg of sulfide electrolyte powder and place it inside the mold battery. Apply 200MPa pressure to obtain a solid electrolyte layer. On one side of the electrolyte layer, add 15mg of composite positive electrode powder and apply 350MPa pressure. Then, on the other side of the electrolyte layer, add silicon-carbon negative electrode composite powder or a negative electrode sheet according to the design of N / P=1.2 and apply 150MPa pressure to assemble a test battery.

[0052] Electrochemical testing Charge / discharge test: At 25℃, first charge at a constant current of 0.1C to 4.25 V, then charge at a constant voltage to 0.02C, and then charge and discharge at a constant current of 0.1C, with a voltage range of 2.5-4.25 V. The charging capacity, discharging capacity, and initial coulombic efficiency (first efficiency) are calculated based on the mass of the positive electrode active material (excluding the mass of the lithium replenishment agent).

[0053] Cyclic test: Cycle 100 times at 1C current between 2.5-4.25 V, and record the capacity retention rate.

[0054] The assembly details are shown in Table 1.

[0055] Table 1 Assembly details of the embodiments and comparative examples

[0056] The test results are shown in Table 2.

[0057] Table 2. Test battery performance of Examples 11-16 and Comparative Examples 11-14

[0058] Table 1 shows that Examples 11 to 15 (lithium supplement + high-silicon anode): initial efficiency 85.7%~88.2%, cycle retention 93%~94%. The introduction of transition metals (Ni / Co) and chalcogen elements (Se / Te) reduces Li... The S-bond energy enables the lithium replenishment agent to rapidly decompose and release lithium ions during the first charge, effectively compensating for the irreversible lithium consumption during the formation of the SEI in the silicon anode. Compared with comparative examples 11 and 12, the first-cycle efficiency is significantly improved. The Ni3S2 and CoS2 products generated after delithiation have good electronic conductivity and mechanical strength, buffering the expansion of the active material. At the same time, the in-situ confined polysulfides ensure long-term interface stability, and the cycle retention rate is significantly improved.

[0059] Example 16 (lithium replenisher + no negative electrode): initial efficiency 83.5%, retention rate 82.6%. The lithium ions released by the lithium replenisher compensate for the double lithium consumption caused by SEI formation and lithium deposition in the no-negative-electrode system, resulting in a significant improvement in initial efficiency and cycle life compared to the comparative example. However, because the lithium replenisher has a high substitution rate of transition metal elements for lithium, the lithium replenishment effect is slightly worse than other examples.

[0060] In Comparative Example 11, the use of pure Li2S as a lithium replenisher resulted in insufficient lithium replenishment due to the high decomposition potential and slow kinetics of Li2S, which was partially undecomposed. Furthermore, both Li2S and the delithiation product elemental sulfur are insulating materials with extremely poor electron conduction, which increases the interfacial impedance.

[0061] Comparative Example 12, lacking a lithium replenisher and without additional lithium source to compensate for SEI consumption, experienced continuous lithium depletion during cycling, resulting in rapid capacity decay.

[0062] Comparative Example 13, lacking lithium replenishment agent and having no negative electrode structure, relies solely on the positive electrode NCM for lithium source. After the first charge, lithium deposition on the surface of the negative electrode carbon fiber generates SEI, consuming a large amount of active lithium. This results in insufficient reversible lithium intercalation of the positive electrode during discharge, leading to a significantly lower initial efficiency. In subsequent cycles, lithium dendrites and dead lithium cause the capacity to collapse rapidly.

[0063] Comparative Example 14 uses a negative electrode lithium replenishment agent, which significantly improves both first-efficiency and cycle performance. However, the current industrialization maturity of the negative electrode pre-lithiation technology is low, and lithium metal or pre-lithiation silicon-carbon materials pose high safety risks.

[0064] In summary, this application weakens the Li-S bond energy and significantly reduces the delithiation overpotential by introducing the transition metal M into the Li₂S lattice. The lithium replenishment agent can rapidly release lithium ions within a voltage window of 2.0-4.3 V, exhibiting electrochemical activity far exceeding that of pure Li₂S. Furthermore, the main framework of the lithium replenishment agent remains sulfide, possessing natural chemical compatibility with sulfide solid electrolytes (such as Li₆PS₅Cl). Unlike oxide lithium replenishment agents, it does not generate high-resistivity byproducts at the interface, thus improving the long-term stability of the interface.

[0065] Introducing Se and / or Te elements optimizes the performance of lithium replenishment agents by leveraging the properties of elements in the same group. Se doping improves the ionic conductivity of the material, while Te doping significantly enhances the electronic conductivity. The synergistic effect of both can further reduce the delithiation overpotential of the lithium replenishment agent and improve lithium replenishment efficiency. Simultaneously, the introduction of Se and Te does not alter the compatibility of the material with sulfide electrolytes, maintaining interfacial stability.

[0066] When applied to electrodeless sulfide-based all-solid-state batteries, the lithium replenishment agent has a high theoretical lithium replenishment capacity, providing a sufficient active lithium source for the electrodeless system. Table 1 shows that, after using the lithium replenishment agent of this application, the initial coulombic efficiency of the electrodeless battery increased from 78.4% to 83.5%, and the capacity retention after 100 cycles increased from 34% to 82%. This significantly solves the short lifespan problem caused by lithium source depletion in electrodeless systems, providing key technical support for achieving ultra-high energy density batteries with >500 Wh / kg.

[0067] Application in silicon-carbon anode sulfide all-solid-state batteries: The lithium replenishing agent of this invention can effectively compensate for the low first-efficiency loss of silicon-carbon anodes. At the same time, the transition metal sulfides in the delithiation products have a certain mechanical flexibility, which helps to alleviate the interfacial stress caused by the volume expansion of positive and negative electrode materials, and further improves the cycle stability of the cell.

[0068] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0069] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0070] In the description of the embodiments of this application, terms such as "exemplary," "for example," or "for instance" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplary," "for example," or "for instance" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary," "for example," or "for instance" is intended to present the relevant concepts in a concrete manner.

[0071] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0072] The above are merely preferred embodiments of this application and do not limit the scope of this application. Any equivalent structural or procedural transformations made based on the description and drawings of this application, or direct or indirect applications in other related technical fields, are similarly included within the scope of protection of this application.

Claims

1. A lithium supplement, characterized in that, A cathode for use in sulfide all-solid-state batteries, comprising at least one of compounds having chemical formula A and chemical formula B, wherein: Chemical formula A is: Li 2-2x M x S 1-y-z Se y Te z M is a transition metal element, 0≤x≤0.5, 0≤y≤0.5, 0≤z≤0.5, x+y+z>0; Chemical formula B is: Li₂S / MS n M is a transition metal element, and MS n It is a transition metal sulfide, 1≤n≤2.

2. The lithium supplement agent as described in claim 1, characterized in that, The transition metal element includes at least one of Ni, Co, Fe, Mn, Cu, Zn, Mo, W, V and Cr.

3. The lithium supplement agent as described in claim 1, characterized in that, The lithium replenishing agent has a particle size of 0.3 μm to 1.5 μm.

4. The lithium supplement agent as described in claim 1, characterized in that, The lithium replenisher has a coating layer on at least a portion of its surface, and the coating layer material includes at least one of carbon, a conductive polymer, and a sulfide electrolyte.

5. A positive electrode material, characterized in that, It includes a positive electrode active material, a sulfide solid electrolyte, a conductive agent, a binder, and a lithium supplement agent as described in claim 1.

6. The cathode material as described in claim 5, characterized in that, The lithium supplement agent accounts for 0.5% to 3% of the mass of the cathode material.

7. A solid-state secondary battery, characterized in that, It includes a positive electrode, a sulfide solid electrolyte layer, and a negative electrode, wherein the positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector, and the positive electrode material layer includes the positive electrode material as described in claim 5.

8. The solid-state secondary battery as described in claim 7, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode material layer includes at least one of silicon-carbon composite materials or at least one of conductive carbon materials.

9. The solid-state secondary battery as described in claim 8, characterized in that: In the silicon-carbon composite material, the mass percentage of silicon is greater than or equal to 30%; or, The conductive carbon material includes at least one of carbon nanotubes, carbon fibers, and hard carbon.

10. An electrical appliance, characterized in that, Including the solid-state secondary battery as described in claim 7.

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