All-solid-state battery
Technical Field
The invention relates to the technical field of new energy, in particular to an all-solid-state battery.
Background
The traditional lithium ion battery adopts organic liquid electrolyte, and under the abnormal conditions of overcharge, internal short circuit and the like, the battery is easy to generate heat, so that the electrolyte is subjected to gas expansion, decomposition, spontaneous combustion and even explosion, potential safety hazards exist, and the battery is also a short plate of the conventional ternary material. The all-solid-state lithium battery based on the solid electrolyte adopts the solid electrolyte, does not contain inflammable and volatile components, thoroughly eliminates the potential safety hazards of battery smoking, ignition and the like caused by liquid leakage of the battery, and is called as the safest battery system.
Therefore, the all-solid-state battery is considered as a lithium battery of the next generation having industrial value. The structure of the all-solid-state battery comprises a positive electrode, a solid-state electrolyte and a negative electrode, and in the actual use process, problems still exist, such as the negative electrode is easy to precipitate lithium. In the charging process of the battery, lithium ions are extracted from the positive electrode and inserted into the negative electrode, but in actual use, if the lithium ions extracted from the positive electrode cannot be inserted into the negative electrode, the lithium ions can only be precipitated on the surface of the negative electrode, so that a grey substance is formed, and the lithium precipitation phenomenon seriously affects the performance of the battery.
CN111009682A discloses an all solid-state lithium ion battery, which includes a first solid-state electrolyte and a second solid-state electrolyte with different thicknesses and roughness, and solves the problems of electrode adhesion and short circuit in solid-state electrolyte design, but the transmission path of lithium ions is different due to the different thicknesses of the solid-state electrolytes, thereby resulting in the problem that the battery is easy to separate lithium during actual use.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an all-solid-state battery which can effectively overcome the problem of lithium precipitation of the all-solid-state battery.
In order to solve the technical problems, the invention provides the following technical scheme:
an all-solid battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode;
the negative electrode comprises a first negative electrode and a second negative electrode which are connected with each other, and the second negative electrode is positioned on the side surface of the first negative electrode;
the positive electrode comprises a first positive electrode and a second positive electrode which are connected with each other, and the second positive electrode is positioned on the side surface of the first positive electrode;
the solid electrolyte layer comprises a first solid electrolyte layer and a second solid electrolyte layer which are connected with each other, the second solid electrolyte layer is positioned on one side of the first solid electrolyte layer, the first solid electrolyte layer is positioned between the first positive electrode and the first negative electrode, and the second solid electrolyte layer is positioned between the second positive electrode and the second negative electrode;
the thickness of the first solid electrolyte layer is smaller than that of the second solid electrolyte layer, and the ionic conductivity of the first solid electrolyte layer is smaller than that of the second solid electrolyte layer;
the first solid electrolyte layer is an oxide solid electrolyte, and the second solid electrolyte layer contains a sulfide solid electrolyte;
the sulfide solid electrolyte includes Li10GeP2S12、xLi2S·(100-x)P2S5 (60≤x≤80)、Li7P3S11、Li6PS5Cl、Li6PS5Br、Li6PS5ClxBr1-x (x=0~1.0)、Li6+xP1-xGexS5I、Li5PS4X2(X = Cl,Br,I)、Li10MP2S12(M=Si,Ge,Sn)、Li5PS4X2(X = Cl,Br,I)、Li9.54Si1.74P1.44S11.7Cl0.3One or more combinations of;
the second positive electrode comprises an active substance layer and a coating layer coated on the active substance layer, the active substance layer adopts an oxide electrode material, and the coating layer adopts a halide solid electrolyte;
the dosage of the halide solid electrolyte is 0.1-0.7wt% of the oxide electrode material;
the halide solid electrolyte is selected from Li3InBr6-xClx(x≤4)、Li3InBr3Cl3、LiInBr4、Li3InBr6、Li3InCl6、Li3YX6 (X=Cl,Br,I)、Li3ErX6 (X=Cl,Br,I)、Li3ScX6 (X=Cl,Br,I)、Li3LaI6、Li3LuCl6、Li3-xEr1-xZrxCl6(x≤0.6)、Li3-xY1-xZrxCl6(x≤0.6)、Li3Y1-xInxCl6 (0 ≤ x < 1)、CsSnCl3、LixScCl3+xThe thickness of the halide solid electrolyte used for coating is 3-20 nm, and the room temperature lithium ion conductivity is more than 10-4 S/cm。
In a preferred embodiment, the oxide electrode material is selected from lithium cobaltate (LiCoO)2) Lithium iron phosphate (LiFePO)4) Ternary positive electrode material (LiNi)1-y-zMnyCozO2(NCM)、LiNi1-y-zAlyCozO2(NCA)) of one or more of the above.
In a preferred embodiment, the roughness of the first solid electrolyte layer is less than the roughness of the second solid electrolyte layer.
In a preferred embodiment, the first positive electrode contains a third solid electrolyte, the second positive electrode contains a fourth solid electrolyte, and the ion conductivity of the fourth solid electrolyte is greater than the ion conductivity of the third solid electrolyte.
In a preferred embodiment, the fourth solid-state electrolyte is a sulfide solid-state electrolyte.
In a preferred embodiment, the all-solid-state battery includes two second negative electrodes, and the two second negative electrodes are respectively disposed on two sides of the first negative electrode in an opposite manner;
the all-solid-state battery comprises two second anodes, and the two second anodes are respectively oppositely arranged on two sides of the first anode;
the all-solid-state battery comprises two second solid-state electrolyte layers, and the two second solid-state electrolyte layers are respectively and oppositely arranged on two sides of the first solid-state electrolyte layer.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
an embodiment of the present invention provides an all-solid-state battery, including a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the negative electrode includes a first negative electrode and a second negative electrode connected to each other, the second negative electrode is disposed on a side of the first negative electrode, the positive electrode includes a first positive electrode and a second positive electrode connected to each other, the second positive electrode is disposed on a side of the first positive electrode, the solid electrolyte layer includes a first solid electrolyte layer and a second solid electrolyte layer connected to each other, the second solid electrolyte layer is disposed on a side of the first solid electrolyte layer, the first solid electrolyte layer is disposed between the first positive electrode and the first negative electrode, the second solid electrolyte layer is disposed between the second positive electrode and the second negative electrode, a thickness of the first solid electrolyte layer is smaller than a thickness of the second solid electrolyte layer, an ion conductivity of the first solid electrolyte layer is smaller than an ion conductivity of the second solid electrolyte layer, in the embodiment, the solid electrolyte layer comprises a battery structure of a first solid electrolyte layer and a second solid electrolyte layer which are connected with each other and arranged side by side, when the thicknesses of the two solid electrolyte layers are different, the ion conductivities of the first solid electrolyte layer and the second solid electrolyte layer can be matched with each other by selecting the first solid electrolyte layer and the second solid electrolyte layer with proper ion conductivities, so that the transmission efficiencies of the two parts tend to be consistent, and the problem of lithium precipitation of the battery is solved;
the second positive electrode comprises an active substance layer and a coating layer coated on the active substance layer, the active substance layer adopts an oxide electrode material, the coating layer adopts a halide solid electrolyte, and the second positive electrode and the first positive electrode are better matched by optimizing the structure and selecting materials of the second positive electrode, selecting a reasonable electrolyte material and adopting a halide solid electrolyte coating mode; in addition, by arranging the coating layer in the second positive electrode, the side reaction between the oxide electrode material and the sulfide solid electrolyte of the second solid electrolyte layer can be effectively inhibited, so that the cycle performance and the rate capability of the all-solid-state lithium ion battery are improved;
it should be noted that the present invention only needs to achieve at least one of the above technical effects.
Drawings
Fig. 1 is a cross-sectional view of an all-solid battery according to embodiments 1 to 7.
The labels in the figure are: 100-all-solid-state battery, 1-negative electrode, 1 a-first negative electrode, 1 b-second negative electrode, 2-positive electrode, 2 a-first positive electrode, 2 b-second positive electrode, 3-solid electrolyte layer, 3 a-first solid electrolyte layer, 3 b-second solid electrolyte layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it is to be understood that the terms "vertical," "parallel," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present invention and for simplicity in description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are not to be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In the prior art, an all-solid-state battery structure generally includes a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode, and the roughness of the solid electrolyte layer has a large influence on an interface formed between the solid electrolyte layer and the positive electrode, and an interface formed between the solid electrolyte layer and the negative electrode, which easily causes contradictions between adhesion, short circuit, and impedance. In view of the above-mentioned contradiction existing in the all-solid-state battery, some technical people have proposed an all-solid-state battery structure, in which the negative electrode includes a first negative electrode and a second negative electrode, the second negative electrode is located on a side surface of the first negative electrode, the solid-state electrolyte layer includes a first solid-state electrolyte layer and a second solid-state electrolyte layer, the first solid-state electrolyte layer is located between the positive electrode and the first negative electrode, the second solid-state electrolyte layer is located between the positive electrode and the second negative electrode, and the roughness of the second solid-state electrolyte layer is greater than that of the first solid-state electrolyte layer.
The all-solid-state battery is provided with the first negative electrode and the second negative electrode which are mutually connected, and the solid electrolyte layer is divided into the first solid electrolyte layer and the second solid electrolyte layer which are mutually connected, so that the roughness of the first solid electrolyte layer corresponding to the first negative electrode is smaller, and the problems of easy short circuit of the battery and larger integral impedance of the battery caused by larger roughness of the solid electrolyte layer are solved; and the roughness of the second solid electrolyte layer corresponding to the second cathode part is larger, so that the problems of the existing all-solid-state battery that the roughness of the solid electrolyte layer is too small and the bonding force between the electrode and the solid electrolyte is not strong are solved. The structure overcomes the problem of difficulty in designing the roughness of the solid electrolyte layer through the combined design of the first cathode, the second cathode, the first solid electrolyte layer and the second solid electrolyte layer.
However, when the second solid electrolyte layer has a relatively large roughness, the dendrite of the second negative electrode may pierce the solid electrolyte to cause a short circuit. The following solutions are further proposed for the new problem: the thickness of the first negative electrode is greater than that of the second negative electrode, and the thickness of the first solid electrolyte layer is less than that of the second solid electrolyte layer.
In the scheme, the cross section area of the first negative electrode is larger than that of the second negative electrode, and the distance between the second negative electrode and the positive electrode is larger than that between the first negative electrode and the positive electrode, so that the adverse factor of short circuit easily caused by the larger roughness of the second electrolyte layer is partially offset, the probability of lithium dendrite passing through the solid electrolyte is lower due to the increased distance between the second negative electrode and the positive electrode, and the larger roughness brings the beneficial effect of the adhesion between the solid electrolyte layer and the negative electrode.
However, this structure brings new problems: since the first solid electrolyte layer is thinner than the second solid electrolyte layer, the lithium ion transmission efficiency of the first solid electrolyte layer and the lithium ion transmission efficiency of the second solid electrolyte layer are different under the condition that the ionic conductivities of the two solid electrolyte layers are the same, so that the lithium is easily separated from the negative electrode layer, and the service performance of the battery is influenced.
On the basis, in view of the above-mentioned influence of the lithium separation phenomenon on the battery performance of the all-solid battery under the structure, the present embodiment provides an all-solid battery, which can effectively solve the problem.
The all-solid battery provided by the present embodiment includes a positive electrode, a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode. The positive electrode comprises a first positive electrode and a second positive electrode which are connected with each other, and the second positive electrode is located on the side face of the first positive electrode. The negative electrode includes a first negative electrode and a second negative electrode connected to each other, and the second negative electrode is located on a side of the first negative electrode. The solid electrolyte layer includes a first solid electrolyte layer and a second solid electrolyte layer connected to each other, and the second solid electrolyte layer is located on one side of the first solid electrolyte layer. And the first solid electrolyte layer is positioned between the first positive electrode and the first negative electrode, and the second solid electrolyte layer is positioned between the second positive electrode and the second negative electrode. The thickness of the first solid electrolyte layer is smaller than that of the second solid electrolyte layer, and the ionic conductivity of the first solid electrolyte layer is smaller than that of the second solid electrolyte layer.
Therefore, in the all-solid-state battery in this embodiment, the first negative electrode and the second negative electrode are arranged, and the solid electrolyte layer is divided into the first solid electrolyte layer and the second solid electrolyte layer, so that the roughness of the first solid electrolyte layer corresponding to the first negative electrode is small, and the problems that the battery is easy to short circuit and the overall impedance of the battery is large due to the large roughness of the solid electrolyte layer can be reduced; the roughness of the second solid electrolyte layer corresponding to the second cathode is larger, so that the problems of small roughness of the solid electrolyte and weak bonding force between the electrode and the solid electrolyte in the existing all-solid-state battery design are solved. Furthermore, the situation that the dendrite of the second negative electrode pierces the second solid electrolyte layer is solved by the fact that the thickness of the first negative electrode is larger than that of the second negative electrode and the thickness of the first solid electrolyte is lower than that of the second solid electrolyte. Most importantly, the ionic conductivity of the first solid electrolyte layer is smaller than that of the second solid electrolyte layer, so that the transmission efficiency of the two parts tends to be consistent, and the phenomenon of lithium precipitation of a negative electrode is effectively avoided.
In the present embodiment, for the measurement of the roughness, an arithmetic average roughness Ra, a maximum height Ry, a ten-point average roughness Rz, and the like may be selected, and preferably, the arithmetic average roughness Ra is used, and the measurement is performed by using GB/T103a-2009 as a test standard, or the surface roughness of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer may be measured by taking an image of the interface of the electrode layer and the solid electrolyte layer by SEM and then using image analysis software.
Specifically, in the present embodiment, the first solid electrolyte layer and the second solid electrolyte layer include different solid electrolyte materials, so that the ionic conductivity of the first solid electrolyte layer is smaller than that of the second solid electrolyte layer. Specifically, the second solid electrolyte layer with a larger thickness adopts a solid electrolyte with high ionic conductivity, and the first solid electrolyte layer with a smaller thickness adopts a solid electrolyte with lower ionic conductivity, so that the ionic conduction efficiencies of the first solid electrolyte layer and the second solid electrolyte tend to be the same.
And it was confirmed through experiments that when the ion conductivities of the first solid electrolyte layer and the second solid electrolyte layer satisfy the following relationship, the negative electrode is less likely to extract lithium:
(S1/S2)3/4=α(L1/L2)
wherein: s1Is the ionic conductivity of the first solid electrolyte layer;
S2is the ionic conductivity of the second solid electrolyte layer;
L1is the thickness of the first solid electrolyte layer;
L2is the thickness of the second solid electrolyte layer;
α=2.5-4.4。
in a preferred embodiment, the first solid electrolyte layer with a smaller thickness contains an oxide solid electrolyte with a smaller ionic conductivity, and the second solid electrolyte layer with a larger thickness contains a sulfide solid electrolyte with a larger ionic conductivity.
Wherein the sulfide solid electrolyte comprises Li10GeP2S12、xLi2S·(100-x)P2S5 (60≤x≤80)、Li7P3S11、Li6PS5Cl、Li6PS5Br、Li6PS5ClxBr1-x(x=0~1.0)、Li6+xP1-xGexS5I、Li5PS4X2(X=Cl,Br,I)、Li10MP2S12(M=Si,Ge,Sn)、Li5PS4X2(X=Cl,Br,I)、Li9.54Si1.74P1.44S11.7Cl0.3One or a combination of more of the same.
Further preferably, the first positive electrode contains a third solid electrolyte, and the second positive electrode contains a fourth solid electrolyte. The ion conductivity of the fourth solid electrolyte is greater than that of the third solid electrolyte, and the content of the fourth solid electrolyte is less than that of the third solid electrolyte. And, as a preferable one, the fourth solid electrolyte is a sulfide solid electrolyte, and the third solid electrolyte is not particularly limited.
Since the second solid electrolyte layer contains a sulfide solid electrolyte having a large ionic conductivity, an interface difference or an ion conduction difference exists between the first positive electrode, the second positive electrode, the first solid electrolyte layer, and the second solid electrolyte layer. For the second positive electrode, it is advantageous to add a small amount of a high ion-conducting sulfide solid electrolyte compared to adding a larger amount of a lower ion-conducting oxide solid electrolyte, while there is no restriction in the first positive electrode to ensure that the first positive electrode and the second positive electrode approach the same ion-conducting efficiency.
In some preferred embodiments, the second positive electrode includes an active material layer and a coating layer coated on the active material layer, the active material layer uses an oxide electrode material, and the coating layer uses a halide solid electrolyte. The halide solid electrolyte coating layer can inhibit the side reaction between the oxide electrode material and the sulfide electrolyte layer, thereby improving the cycle performance and rate capability of the all-solid battery.
Preferably, the halide solid electrolyte is used in an amount of 0.1 to 0.7wt% of the oxide electrode material, and more preferably, the halide solid electrolyte is used in an amount of 0.1 to 0.4wt% of the oxide electrode material.
Wherein the halide solid electrolyte is selected from Li3InBr6-xClx(x≤4)、Li3InBr3Cl3、LiInBr4、Li3InBr6、Li3InCl6、Li3YX6 (X=Cl,Br,I)、Li3ErX6 (X=Cl,Br,I)、Li3ScX6 (X=Cl,Br,I)、Li3LaI6、Li3LuCl6、Li3-xEr1-xZrxCl6(x≤0.6)、Li3-xY1-xZrxCl6(x≤0.6)、Li3Y1-xInxCl6(0 ≤ x < 1)、CsSnCl3、LixScCl3+xThe thickness of the halide solid electrolyte used for coating is 3-20 nm, and the room temperature lithium ion conductivity is more than 10-4 S/cm。
In this example, the oxide electrode material is a positive electrode active material and can release capacity. The selection of the oxide electrode material is not particularly limited, and examples thereof include lithium cobaltate (LiCoO)2) Lithium iron phosphate (LiFePO)4) Ternary positive electrode material (LiNi)1-y- zMnyCozO2(NCM)、LiNi1-y-zAlyCozO2(NCA)) of one or more of the above.
Further, the sulfide solid electrolyte has a relatively active property with respect to the oxide solid electrolyte, and easily reacts with the positive electrode active material, and thus, it is advantageous to coat the positive electrode active material with an ion conductivity of less than 10 compared to the conventional one-4Oxide coating of S/cm, halide solid stateThe electrolyte used as the coating layer has the advantages of high ion conductivity and small coating amount, and the matching property of the second positive electrode and the second solid electrolyte layer can be effectively improved by coating the positive electrode active material with halide.
In addition, since the ion conduction path of the second solid electrolyte layer is long, there is a high demand for the ion conductivity of the second solid electrolyte layer and the second positive electrode, and at the same time, the second positive electrode should have ion conductivity close to that of the first positive electrode, which allows a considerable matching in ion conductivity between the second positive electrode and the second solid electrolyte layer, and thus, it is advantageous to use a sulfide solid electrolyte having high ion conductivity.
In a specific embodiment, the all-solid-state battery includes two second negative electrodes, and the two second negative electrodes are respectively disposed on two sides of the first negative electrode in an opposite manner. The all-solid-state battery comprises two second anodes, and the two second anodes are respectively and oppositely arranged on two sides of the first anode. The second solid electrolyte layer is located on both sides of the first solid electrolyte layer, and the second solid electrolyte layer is in contact with the first solid electrolyte layer, such as a cylindrical battery. Furthermore, the all-solid-state battery comprises two second solid-state electrolyte layers, and the two second solid-state electrolyte layers are respectively arranged on two sides of the first solid-state electrolyte layer in an opposite mode. In the structure, the thickness of the first solid electrolyte layer is smaller than that of the second solid electrolyte layer, and the ionic conductivity of the first solid electrolyte layer is smaller than that of the second solid electrolyte layer.
On the basis of the scheme, further: the cross-sectional area of the first negative electrode is larger than that of each of the second negative electrodes, and the thickness of the first negative electrode is larger than that of each of the second negative electrodes.
Preferably, the difference between the thickness of the second negative electrode and the thickness of the first negative electrode is in the range of 20 to 400% of the thickness of the first solid electrolyte layer, and the selection of the numerical value range can be adjusted according to the requirements of the battery. As an operational solution, the range of values may be 20-150% when the battery performance is emphasized. As another operational solution, the range of values may be 200-400% with security concerns.
The skilled person will understand that in general the difference in thickness of the second negative electrode and the first negative electrode should be equal to the difference in thickness of the first solid-state electrolyte layer and the second solid-state electrolyte layer, in principle there being only a slight difference within the error range.
For some cases, the thickness difference between the second negative electrode and the first negative electrode is not equal to the thickness difference between the first solid electrolyte layer and the second solid electrolyte layer, for example, the thickness of the first negative electrode and the second negative electrode is affected by the presence of other components in the first solid electrolyte layer or the portion of the second solid electrolyte layer in corresponding contact with the first negative electrode and the second negative electrode. Preferably, the anode active material layer of the first anode and the anode active material layer of the second anode have the same thickness, and the overall thickness difference of the first anode and the second anode may be provided by the thickness difference of the current collectors.
It is understood that the first negative electrode, the second negative electrode, the first solid electrolyte layer, the second solid electrolyte layer, the first positive electrode and the second positive electrode all refer to the whole, the whole refers to the whole formed by the current collector and the active material layer, various transition layers or functional layers arranged between the current collector and the active material layer, the multiple active material layers are all regarded as a part of the whole of the positive electrode or the negative electrode, the thickness of the coating or other doped components arranged on the first negative electrode, the second negative electrode, the first solid electrolyte layer, the second solid electrolyte layer, the first positive electrode and the second positive electrode is regarded as the thickness of the corresponding whole, such as the coating arranged on the negative electrode, and the corresponding coating thickness is understood as a part of the thickness of the corresponding whole negative electrode, and the scheme thereof is not considered to be excluded from the protection scope of the present application.
It should be further noted that, when the roughness of the first solid electrolyte layer and the roughness of the second solid electrolyte layer have a difference, the safety and the bonding strength should be considered comprehensively, and within a reasonable range, a larger roughness may increase the bonding strength between the solid electrolyte layer and the negative electrode, but an excessively large roughness may promote the formation of lithium dendrites and further cause short circuits, whereas an excessively small roughness may prevent the bonding force from falling off due to insufficient safety; therefore, the roughness of the first solid electrolyte layer is designed to satisfy safety mainly, while the roughness of the second solid electrolyte layer is designed to consider cohesive force mainly, and since the distance between the second negative electrode and the second positive electrode is longer than that between the first negative electrode and the first positive electrode, even if the roughness is increased, safety can be ensured.
Therefore, it is advantageous to design in this embodiment that the surface roughness of the second solid state electrolyte layer is greater than the surface roughness of the first solid state electrolyte layer. The roughness may be adjusted according to the actual formulation system, and preferably, the surface roughness of the first solid electrolyte layer ranges from 0.1 to 30 μm in value, and the surface roughness of the second solid electrolyte layer ranges from 0.1 to 50 μm in value, preferably 10 to 15 μm in value.
It should be noted, however, that the roughness of the first solid electrolyte layer is not as low as possible, and experiments have confirmed that, in the case of the solid electrolyte layer, too low roughness may rather promote the formation of lithium dendrites, thereby affecting safety.
In a preferred embodiment, the roughness of both the first solid electrolyte layer and the second solid electrolyte layer is greater than the surface roughness of the negative electrode, and the difference between the roughness of the second solid electrolyte layer and the roughness of the second negative electrode is greater than the difference between the roughness of the first solid electrolyte layer and the roughness of the first negative electrode.
Preferably, the difference between the roughness of the second solid electrolyte layer and the roughness of the second negative electrode is greater than the difference between the roughness of the first solid electrolyte layer and the roughness of the first negative electrode by 100-. Preferably, the difference between the roughness of the second solid state electrolyte layer and the roughness of the second negative electrode is greater than the difference between the roughness of the first solid state electrolyte layer and the roughness of the first negative electrode by 200-.
Specifically, the existing electrodes and the solid electrolyte layer are generally bonded by a powder pressing process, so that the difference of appropriate roughness between the electrodes and the solid electrolyte layer is beneficial to improving the bonding strength, but the excessive roughness difference affects the bonding strength; meanwhile, in the present embodiment, since the first solid electrolyte layer and the second solid electrolyte layer have different binding forces with the negative electrode, the stress reserved between the negative electrode and the solid electrolyte layer gradually accumulates along with the expansion of the negative electrode during the actual use. Therefore, in the present embodiment, the difference between the roughness of the second solid state electrolyte layer and the roughness of the second negative electrode is greater than the difference between the roughness of the first solid state electrolyte layer and the roughness of the first negative electrode by 100-.
In addition, the solid electrolyte layer should satisfy the condition that the roughness of the second solid electrolyte layer is 30-150% larger than that of the first solid electrolyte layer, so that the bonding force and stress accumulation between the solid electrolyte layer and the negative electrode can be properly treated, and the stress concentration of the battery can not occur in the service life.
Preferably, the difference between the roughness of the second solid electrolyte layer and the roughness of the second negative electrode is 200-300% greater than the difference between the roughness of the first solid electrolyte layer and the roughness of the first negative electrode, and the roughness of the second solid electrolyte layer is 50-100% greater than the roughness of the first solid electrolyte layer, so that the safety guarantee of the battery is further improved.
Preferably, the roughness of the second negative electrode is greater than the roughness of the first negative electrode.
As a preferred solution of this embodiment, the current collector materials in the positive electrode and the negative electrode independently include any one or a combination of more of aluminum, copper, nickel, or zinc. Preferably, the positive electrode uses aluminum as a current collector, and the negative electrode uses copper as a current collector.
As a preferred embodiment of this example, the first positive electrode includes a positive electrode active material, and the positive electrode active material of the first positive electrode is not particularly limited and includes LiCoO2、LiMnO2、LiNiO2、LiVO2、LiNi1/3Co1/3Mn1/3O2、LiMn2O4、LiTi5O12、Li(Ni0.5Mn1.5)O4、LiFePO4、LiMnPO4、LiNiPO4、LiCoPO4Or LiNbO3Any one or a combination of at least two of them.
Among them, LiCoO2、LiMnO2、LiNiO2、LiVO2、LiNi1/3Co1/3Mn1/3O2Having a rock-salt layered structure, LiMn2O4、LiTi5O12、Li(Ni0.5Mn1.5)O4Having a spinel structure, LiFePO4、LiMnPO4、LiNiPO4、LiCoPO4、LiNbO3Has an olivine structure. Also, known coating forms may be used, such as LiNbO3Etc. to coat the material.
Preferably, the positive electrode active material layer of the first positive electrode further includes any one of a solid electrolyte material, a conductive material, or a binder material, or a combination of at least two thereof. The solid electrolyte material includes a sulfide solid electrolyte material and/or an oxide solid electrolyte layer material. Preferably, the solid electrolyte material is an oxide solid electrolyte. The conductive material includes any one of acetylene black, conductive carbon black, ketjen black, or carbon fiber or a combination of at least two thereof. The bonding material comprises any one or the combination of at least two of vinylidene fluoride, sodium carboxymethyl cellulose or styrene butadiene rubber.
The thickness of the active material layer of the first positive electrode and the second positive electrode is preferably 1 to 500. mu.m, for example, 1. mu.m, 5. mu.m, 10. mu.m, 50. mu.m, 100. mu.m, 200. mu.m, 300. mu.m, 400. mu.m, 500. mu.m, etc., and preferably 50 to 200. mu.m.
Preferably, the surface of the positive electrode active material layer of the first positive electrode is coated with a coating layer. The purpose of the surface coating of the positive electrode active material layer of the first positive electrode is to suppress the reaction between the positive electrode active material and the solid electrolyte material.
The coating layer of the first positive electrode is not particularly limited, and any known coating layer coating method can be used in the present embodiment without departing from the concept of the present invention. Preferably, the material of the coating comprises LiNbO3、Li3PO4Or a combination of at least two of LiPON. The thickness of the coating is 1-20nm, such as 1nm, 2nm, 5nm, 8nm, 10nm, 12nm, 14nm, 16nm, 18nm, or 20nm, etc.
Of course, in order to prevent the positive electrode active material of the first positive electrode from reacting with the solid electrolyte layer or the solid electrolyte in the first positive electrode, it is also possible to coat the positive electrode active material of the first positive electrode, the material of the coating is not particularly limited, and any known coating method can be used in the present embodiment.
As an implementation manner of this embodiment, when the thicknesses of the first negative electrode and the second negative electrode are different, the thicknesses of the first positive electrode and the second positive electrode are adjusted so that the thickness of the second positive electrode is smaller than that of the first positive electrode to correspond to the thickness difference between the first negative electrode and the second negative electrode, so as to match the capacities between the positive electrode and the negative electrode, and overcome the problem of lithium deposition.
As a preferable mode of this embodiment, the negative electrode active material layer of the negative electrode includes a negative electrode active material.
Preferably, the anode active material includes any one of a metal active material, a carbon active material, or an oxide active material, or a combination of at least two thereof. The metal active substance comprises any one or the combination of at least two of Si, Sn, In, Si-Al alloy or Si-In alloy. The carbon active material includes any one of graphite, hard carbon or soft carbon or a combination of at least two of them.
Preferably, the oxide active material includes Li4Ti5O12。
Preferably, the anode active material layer further includes any one of a solid electrolyte material, a conductive material, or a binder material or a combination of at least two thereof.
Preferably, the solid electrolyte material includes a sulfide solid electrolyte material and/or an oxide solid electrolyte layer material. Preferably, the conductive material includes any one of acetylene black, conductive carbon black, ketjen black, or carbon fiber, or a combination of at least two thereof. Preferably, the adhesive material comprises any one of or a combination of at least two of vinylidene fluoride, sodium carboxymethylcellulose or styrene butadiene rubber. Preferably, the thickness of the negative electrode active material layer is 1 to 500. mu.m, for example, 1. mu.m, 5. mu.m, 10. mu.m, 50. mu.m, 100. mu.m, 200. mu.m, 300. mu.m, 400. mu.m, 500. mu.m, etc., preferably 50 to 200. mu.m.
Preferably, the first negative electrode and the second negative electrode share the same current collector.
As one preference, the second anode is provided with an active material layer, preferably, both the first anode and the second anode are provided with active material layers, and the active material compositions of both may be the same or different;
on the basis that the second negative electrode is provided with the active material layer, the thickness of the second negative electrode can be adjusted by the thickness of the active material layer or the thickness of the foil, for example, the thickness of the foil of the second negative electrode can be the same as that of the first negative electrode, and the thickness of the second negative electrode is smaller than that of the first negative electrode only by making the thickness of the active material layer different from that of the first negative electrode; on the other hand, the thickness of the active material layer of the second negative electrode may be the same as that of the first negative electrode, and the thickness of the second negative electrode is made smaller than that of the first negative electrode by adjusting the thickness of the foil; the thicknesses of the active material layer and the foil may be adjusted at the same time so that the overall thickness of the second anode is smaller than that of the first anode; even, the foil or the active material layer may be made thicker than the first anode and the other smaller than the first anode, so that the overall thickness of the second anode is smaller than the first anode.
In summary, any reasonable solution that makes the thickness of the second negative electrode smaller than that of the first negative electrode is feasible, and only the battery can be ensured to operate normally.
In the present invention, the material of the solid electrolyte layer located between the positive electrode and the negative electrode may be a crystalline material or an amorphous material. The solid electrolyte layer may be glass or crystallized glass.
Preferably, the thickness of the first solid electrolyte layer located between the cathode and the anode is 10-300 μm, such as 10 μm, 50 μm, 100 μm, 200 μm or 300 μm, etc. Further preferably, the thickness of the first solid electrolyte layer located between the first positive electrode and the first negative electrode is 20 to 60 μm. The range not only satisfies the trend of thinning the solid electrolyte layer, but also can inhibit the short circuit of the anode and the cathode caused by dendrite.
The all-solid battery is further described below with reference to specific embodiments.
Example 1
As shown in fig. 1, the present embodiment provides an all-solid battery 100, the all-solid battery 100 including a negative electrode 1, a positive electrode 2, and a solid electrolyte layer 3 between the positive electrode 2 and the negative electrode 1. The negative electrode 1 includes a first negative electrode 1a and two second negative electrodes 1b, and the two second negative electrodes 1b are located on opposite sides of the first negative electrode 1a and are respectively connected to the first negative electrode 1 a. The positive electrode 2 includes a first positive electrode 2a and two second positive electrodes 2b, and the two second positive electrodes 2b are located on opposite sides of the first positive electrode 2a and respectively connected to the first positive electrode 2 a. The solid electrolyte layer 3 includes a first solid electrolyte layer 3a and two second solid electrolyte layers 3b, the two second solid electrolyte layers 3b being respectively located on opposite sides of the first solid electrolyte layer 3a and respectively adjoining the first solid electrolyte layer 3 a. The first solid electrolyte layer 3a is positioned between the first anode 2a and the first cathode 1a, the second solid electrolyte layer 3b is positioned between the second anode 2b and the second cathode 1b, one second cathode 1b corresponds to one second solid electrolyte layer 3b, and the roughness of each second solid electrolyte layer 3b is larger than that of the first solid electrolyte layer 3 a.
The second cathodes 1b have two parts in total, the roughness is 8 mu m, and the thickness is 120 mu m; the first negative electrode 1a had a roughness of 10 μm and a thickness of 150. mu.m. The current collectors of the first negative electrode 1a and the second negative electrode 1b are both copper foils, and the negative active material layers on the current collectors are 60wt% of carbon fibers and 40wt% of polytetrafluoroethylene.
The first positive electrode 2a and the second positive electrode 2b adopt the same current collector, the current collector is aluminum foil, and the composition of the first positive electrode active material layer on the current collector is 90wt% LiCoO23wt% of conductive carbon black, 2wt% of polytetrafluoroethylene, 5wt% of lithium lanthanum zirconium oxide, and the composition of the second positive electrode active material layer is 91wt% of LiCoO24% by weight of conductive carbon black, 3% by weight of polytetrafluoroethylene, 2% by weight of Li6PS5Cl, and LiCoO2With Li3InCl6Coating, wherein the coating amount is 0.7 wt%;
in this example, the thickness of the active material layer of each of the first positive electrode 2a and the second positive electrode 2b was 150 μm.
The material of the first solid electrolyte layer 3a was 95 wt% Li7La3Zr2O125% by weight of polyethylene oxide, thickDegree L 1100 μm and a roughness of 12 μm; the material of both of the two second solid electrolyte layers 3b was 90wt% LGPS (representing Li)10GeP2S12Same below), 10% by weight of polyethylene oxide, thickness L2Both had a roughness of 150 μm and both had a roughness of 18 μm.
The ion conductivities of the first solid electrolyte layer 3a and the second solid electrolyte layer 3b in this all-solid battery 100 satisfy the following relationship: (S)1/S2)3/4=3(L1/L2) In which S is1Is the ionic conductivity of the first solid electrolyte layer; s2Is the ionic conductivity of the second solid electrolyte layer, and S1/S2<1, and L1/ L2=2/3。
Example 2
The battery of this example had the same structure as the battery of example 1, and:
the second cathodes 1b have two parts in total, the roughness is 8 mu m, and the thickness is 120 mu m; the first negative electrode 1a had a roughness of 10 μm and a thickness of 150. mu.m.
The current collectors of the first negative electrode 1a and the second negative electrode 1b are both copper foils, and the negative active material layers on the current collectors are 60wt% of carbon fibers and 40wt% of polytetrafluoroethylene.
The first positive electrode 2a and the second positive electrode 2b adopt the same current collector, the current collector is aluminum foil, and the composition of the first positive electrode active material layer on the current collector is 90wt% LiCoO23wt% of conductive carbon black, 2wt% of polytetrafluoroethylene, 5wt% of lithium lanthanum zirconium oxide, and the composition of the second positive electrode active material layer is 91wt% of LiCoO24% by weight of conductive carbon black, 3% by weight of polytetrafluoroethylene, 2% by weight of Li6PS5Cl,LiCoO2With Li3InCl6Coating, wherein the coating amount is 0.7 wt%;
the thickness of the active material layer of each of the first positive electrode 2a and the second positive electrode 2b was 150 μm.
The material of the first solid electrolyte layer 3a was 95 wt% Li7La3Zr2O125% by weight of polyethylene oxide, thickness L 1100 μm and a roughness of 12 μm; the material of both the second solid electrolyte layers 3b was 95 wt% LGPS; 5wt% polyethylene oxide, thickness L2Both had a roughness of 150 μm and both had a roughness of 18 μm.
The ion conductivities of the first solid electrolyte layer 3a and the second solid electrolyte layer 3b in this all-solid battery 100 satisfy the following relationship: (S)1/S2)3/4=2.5(L1/L2) (ii) a Wherein S is1/S2<1, and L1/ L2=2/3。
Example 3
The battery of this example had the same structure as the battery of example 1, and:
the second cathodes 1b have two parts in total, the roughness is 8 mu m, and the thickness is 120 mu m; the first negative electrode 1a had a roughness of 10 μm and a thickness of 150. mu.m.
The current collectors of the first negative electrode 1a and the second negative electrode 1b are both copper foils, and the negative active material layers on the current collectors are 60wt% of carbon fibers and 40wt% of polytetrafluoroethylene.
The first positive electrode 2a and the second positive electrode 2b adopt the same current collector, the current collector is aluminum foil, and the composition of the first positive electrode active material layer on the current collector is LiCoO with 90wt%23wt% of conductive carbon black, 2wt% of polytetrafluoroethylene, 5wt% of lithium lanthanum zirconium oxide, and the composition of the second positive electrode active material layer is 91wt% of LiCoO24% by weight of conductive carbon black, 3% by weight of polytetrafluoroethylene, 2% by weight of Li6PS5Cl, said LiCoO2With Li3InCl6Coating, wherein the coating amount is 0.7 wt%;
the thickness of the active material layer of each of the first positive electrode 2a and the second positive electrode 2b was 150 μm.
The material of the first solid electrolyte layer 3a was 95 wt% Li7La3Zr2O125% by weight of polyethylene oxide, thickness L 1100 μm and a roughness of 12 μm; the material of both the second solid electrolyte layers 3b was 98 wt% LGPS; 2% by weight of polyethylene oxide, thickness L2Both had a roughness of 150 μm and both had a roughness of 18 μm.
The ion conductivities of the first solid electrolyte layer 3a and the second solid electrolyte layer 3b in this all-solid battery 100 satisfy the following relationship: (S)1/S2)3/4=1.8(L1/L2). Wherein S is1/S2<1, and L1/ L2=2/3。
Example 4
The battery of this example had the same structure as the battery of example 1, and:
the second cathodes 1b have two parts in total, the roughness is 8 mu m, and the thickness is 120 mu m; the first negative electrode 1a had a roughness of 10 μm and a thickness of 150. mu.m.
The current collectors of the first negative electrode 1a and the second negative electrode 1b are both copper foils, and the negative active material layers on the current collectors are 60wt% of carbon fibers and 40wt% of polytetrafluoroethylene.
The first positive electrode 2a and the second positive electrode 2b adopt the same current collector, the current collector is aluminum foil, and the composition of the first positive electrode active material layer on the current collector is 90wt% LiCoO23wt% of conductive carbon black, 2wt% of polytetrafluoroethylene, 5wt% of lithium lanthanum zirconium oxide, and the composition of the second positive electrode active material layer is 91wt% of LiCoO24% by weight of conductive carbon black, 3% by weight of polytetrafluoroethylene, 2% by weight of Li6PS5Cl, said LiCoO2With Li3InCl6Coating, wherein the coating amount is 0.7 wt%;
the thickness of the active material layer of each of the first positive electrode 2a and the second positive electrode 2b was 150 μm.
The material of the first solid electrolyte layer 3a was 95 wt% Li7La3Zr2O125% by weight of polyethylene oxide, thickness L 1100 μm and a roughness of 12 μm; the material of both the second solid electrolyte layers 3b was 85 wt% LGPS; 15% by weight of polyethylene oxide, thickness L2Both had a roughness of 150 μm and both had a roughness of 18 μm.
The ion conductivities of the first solid electrolyte layer 3a and the second solid electrolyte layer 3b in this all-solid battery 100 satisfy the following relationship: (S)1/S2)3/4=5(L1/L2). Wherein S is1/S2<1, and L1/ L2=2/3。
Example 5
The battery of this example had the same structure as the battery of example 1, and:
the second cathodes 1b have two parts in total, the roughness is 8 mu m, and the thickness is 120 mu m; the first negative electrode 1a had a roughness of 10 μm and a thickness of 150. mu.m.
The current collectors of the first negative electrode 1a and the second negative electrode 1b are both copper foils, and the negative active material layers on the current collectors are 60wt% of carbon fibers and 40wt% of polytetrafluoroethylene.
The first positive electrode 2a and the second positive electrode 2b adopt the same current collector, the current collector is aluminum foil, and the composition of the first positive electrode active material layer on the current collector is LiCoO with 90wt%23wt% of conductive carbon black, 2wt% of polytetrafluoroethylene, 5wt% of lithium lanthanum zirconium oxide, and the composition of the second positive electrode active material layer is 91wt% of LiCoO24% by weight of conductive carbon black, 3% by weight of polytetrafluoroethylene, 2% by weight of Li6PS5Cl, said LiCoO2With Li3InCl6Coating, the coating amount is 0.4 wt%.
The thickness of the active material layer of each of the first positive electrode 2a and the second positive electrode 2b was 150 μm.
The material of the first solid electrolyte layer 3a was 95 wt% Li7La3Zr2O125% by weight of polyethylene oxide, thickness L 1100 μm and a roughness of 12 μm; the material of both the second solid electrolyte layers 3b is 90wt% LGPS; 10% by weight of polyethylene oxide, thickness L2Both had a roughness of 150 μm and both had a roughness of 18 μm.
The ion conductivities of the first solid electrolyte layer 3a and the second solid electrolyte layer 3b in this all-solid battery 100 satisfy the following relationship: (S)1/S2)3/4=3(L1/L2). Wherein S is1/S2<1, and L1/ L2=2/3。
Example 6
The battery of this example had the same structure as the battery of example 1, and:
the second cathodes 1b have two parts in total, the roughness is 8 mu m, and the thickness is 120 mu m; the first negative electrode 1a had a roughness of 10 μm and a thickness of 150. mu.m.
The current collectors of the first negative electrode 1a and the second negative electrode 1b are both copper foils, and the negative active material layers on the current collectors are 60wt% of carbon fibers and 40wt% of polytetrafluoroethylene.
The first positive electrode 2a and the second positive electrode 2b adopt the same current collector, the current collector is aluminum foil, and the composition of the first positive electrode active material layer on the current collector is LiCoO with 90wt%23wt% of conductive carbon black, 2wt% of polytetrafluoroethylene, 5wt% of lithium lanthanum zirconium oxide, and the composition of the second positive electrode active material layer is 91wt% of LiCoO24% by weight of conductive carbon black, 3% by weight of polytetrafluoroethylene, 2% by weight of Li6PS5Cl, said LiCoO2With Li3InCl6Coating, wherein the coating amount is 1 wt%;
the thickness of the active material layer of each of the first positive electrode 2a and the second positive electrode 2b was 150 μm.
The material of the first solid electrolyte layer 3a was 95 wt% Li7La3Zr2O125% by weight of polyethylene oxide, having a thickness L 1100 μm and a roughness of 12 μm; the material of both the second solid electrolyte layers 3b is 90wt% LGPS; 10% by weight of polyethylene oxide, thickness L2Both had a roughness of 150 μm and both had a roughness of 18 μm.
The ion conductivities of the first solid electrolyte layer 3a and the second solid electrolyte layer 3b in this all-solid battery 100 satisfy the following relationship: (S)1/S2)3/4=3(L1/L2). Wherein S is1/S2<1, and L1/ L2=2/3。
Example 7
The battery of this example had the same structure as the battery of example 1, and:
the second cathodes 1b have two parts in total, the roughness is 8 mu m, and the thickness is 120 mu m; the first negative electrode 1a had a roughness of 10 μm and a thickness of 150. mu.m. The current collectors of the first negative electrode 1a and the second negative electrode 1b are both copper foils, and the negative active material layers on the current collectors are 60wt% of carbon fibers and 40wt% of polytetrafluoroethylene.
The first positive electrode 2a and the second positive electrode 2b adopt the same current collector, the current collector is aluminum foil, and the composition of the first positive electrode active material layer on the current collector is 90wt% LiCoO23wt% of conductive carbon black, 2wt% of polytetrafluoroethylene, 5wt% of lithium lanthanum zirconium oxide, and a second positive electrode active material layerTo 91wt% LiCoO24% by weight of conductive carbon black, 3% by weight of polytetrafluoroethylene, 2% by weight of Li6PS5Cl;
In this example, the thickness of the active material layer of each of the first positive electrode 2a and the second positive electrode 2b was 150 μm.
The material of the first solid electrolyte layer 3a was 95 wt% Li7La3Zr2O125% by weight of polyethylene oxide, having a thickness L 1100 μm and a roughness of 12 μm; the material of both the two second solid electrolyte layers 3b is 90wt% LGPS (Li)10GeP2S12Same below), 10% by weight of polyethylene oxide, thickness L2Both had a roughness of 150 μm and both had a roughness of 18 μm.
The ion conductivities of the first solid electrolyte layer 3a and the second solid electrolyte layer 3b in this all-solid battery 100 satisfy the following relationship: (S)1/S2)3/4=3(L1/L2) In which S is1Is the ionic conductivity of the first solid electrolyte layer; s2Is the ionic conductivity of the second solid electrolyte layer. Wherein S1/S2<1, and L1/ L2=2/3。
The test method comprises the following steps:
and testing the rate performance of the battery at the temperature of 60-80 ℃, wherein the charging rate is 4C, the discharging rate is 8C, and the voltage range is 3-4.3V.
The battery after the cycle test is tested for capacity retention rate and lithium deposition on the surface of the second negative electrode, and the test results are shown in the following table 1:
TABLE 1 Battery Performance test results
As can be seen from the above examples, the all-solid batteries provided in examples 1 to 7 have the same structure and size, and the first efficiency, the 10-cycle capacity retention rate, the 30-cycle capacity retention rate, and the lithium deposition on the negative electrode of the all-solid battery were examined by using the content of the sulfide solid electrolyte in the second solid electrolyte layer and the coating rate of the halide solid electrolyte in the second positive electrode on the active material layer as variables.
It can be seen from examples 1 to 4 that, under the same second positive electrode coating rate, when the content of the sulfide solid electrolyte in the second solid electrolyte layer is within a certain range, no lithium deposition occurs in the negative electrode (examples 1 to 3), and when the content of the sulfide solid electrolyte in the second solid electrolyte layer is low, lithium deposition occurs (example 4). However, when the sulfide solid electrolyte content in the second solid electrolyte layer is within this range, although lithium is not precipitated, the indices such as battery efficiency do not show a single increase in accordance with the increase in the sulfide solid electrolyte content in the second solid electrolyte layer, but have an optimum sulfide solid electrolyte content corresponding to the optimum battery performance, and as the content continues to increase, the battery performance decreases.
It is advantageous that the lithium ion conductive property of the second solid electrolyte layer is higher than that of the lithium ion solid electrolyte layer of the first solid electrolyte layer under the all-solid-state battery structure, particularly when the thickness ratio is within a specific range, i.e., satisfies (S)1/S2)3/4=α(L1/L2) When the lithium ion battery is used (alpha =2.5-4.4), the problem of lithium precipitation of the battery can be effectively solved.
As can be seen from examples 1, 6, and 7, when the sulfide solid electrolyte content in the second solid electrolyte layer was the same (the conductivity of the second solid electrolyte layer was determined), the reaction of the positive electrode active material with the sulfide solid electrolyte was effectively prevented when the second positive electrode was coated with the halide solid electrolyte, and a smaller coating amount (0.7wt%) resulted in better battery performance. Further, it can be seen from examples 1 and 6 that the increase of the coating amount does not significantly improve the safety performance.
Example 8
Corresponding to the products in embodiments 1 to 7, this embodiment provides a method for preparing an all-solid battery, including the steps of:
and S1, respectively coating the first positive electrode slurry and the second positive electrode slurry which are prepared in advance on a first positive electrode current collector and a second positive electrode current collector, and drying to obtain a positive electrode piece comprising a first positive electrode and a second positive electrode.
Preferably, in the second positive electrode, the second positive electrode slurry includes a sulfide solid electrolyte, and the positive electrode active material is coated with a halide solid electrolyte after the second positive electrode is obtained.
S2, respectively coating the first solid electrolyte layer slurry and the second solid electrolyte layer slurry which are prepared in advance on a first positive electrode and a second positive electrode to form a first solid electrolyte layer and a second solid electrolyte layer, so that the thickness of the first solid electrolyte layer and the thickness of the second solid electrolyte layer are smaller than that of the second solid electrolyte layer, and the ionic conductivity of the first solid electrolyte layer is smaller than that of the second solid electrolyte layer, so as to obtain a positive electrode-solid electrolyte layer composite pole piece;
s3, coating the first negative electrode slurry and the second negative electrode slurry which are prepared in advance on the current collectors of the first negative electrode and the second negative electrode, and drying to obtain a negative electrode piece comprising the first negative electrode and the second negative electrode;
and S4, attaching the positive electrode-solid electrolyte layer composite pole piece obtained in the step S2 and the negative electrode pole piece obtained in the step S3 to obtain the all-solid-state battery.
Therefore, the preparation method also comprises the pre-preparation processes of the first anode slurry and the second anode slurry, the first solid electrolyte layer slurry and the second solid electrolyte layer slurry, and the first cathode slurry and the second cathode slurry.
In addition, the pre-preparation process of the above materials is a general preparation method in the field, and is not described in detail in this embodiment. It should be noted that, the preparation method in this embodiment is used for preparing the all-solid-state batteries in embodiments 1 to 7, and the obtained battery structures and battery performances further refer to the descriptions in embodiments 1 to 7, which are not described herein again.
All the above optional technical solutions may be combined arbitrarily to form optional embodiments of the present invention, that is, any multiple embodiments may be combined to meet the requirements of different application scenarios, which are within the protection scope of the present application and are not described herein again.
It should be understood that the above-mentioned embodiments are merely preferred embodiments of the present invention, and not intended to limit the present invention, and any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.