CN111952588B - Lithium battery with buffer layer and preparation method thereof - Google Patents
Lithium battery with buffer layer and preparation method thereof Download PDFInfo
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- CN111952588B CN111952588B CN201910401009.6A CN201910401009A CN111952588B CN 111952588 B CN111952588 B CN 111952588B CN 201910401009 A CN201910401009 A CN 201910401009A CN 111952588 B CN111952588 B CN 111952588B
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- H01M4/00—Electrodes
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- H—ELECTRICITY
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H01M4/02—Electrodes composed of, or comprising, active material
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Abstract
The invention provides a lithium battery with a buffer layer, wherein the buffer layer comprises a barrier buffer layer and/or a cladding buffer layer, wherein the barrier buffer layer is a coating layer positioned between a positive electrode and an electrolyte of the lithium battery; the coated buffer layer is a coating layer coated on the surface of the positive electrode active material particles and/or the solid electrolyte particles, wherein the buffer layer is composed of a proton conductor containing a hydrogen element, and the chemical formula of the proton conductor containing the hydrogen element is as follows: AH of x P y O 1/2+x/2+5y/2 Wherein x is more than 0 and less than or equal to 2, y is more than or equal to 0.8 and less than or equal to 2, A is one or more of Li, na, K, rb and Cs.
Description
Technical Field
The invention relates to a lithium battery with a buffer layer and a preparation method thereof.
Background
Lithium ion secondary batteries (hereinafter, simply referred to as "lithium batteries") have been used as power sources for small electric devices such as portable devices. A lithium battery includes a positive electrode layer, a negative electrode layer, and an electrolyte layer through which lithium ions are conducted between the positive electrode layer and the negative electrode layer.
In recent years, long life and safety have been sought in lithium batteries, and these properties are closely related to continuous side reactions between the positive electrode material and the electrolyte. Especially for all solid-state lithium batteries, for example: the all solid-state lithium battery composed of a sulfide has a problem of low discharge capacity (i.e., poor output characteristics). The reason for this is that, since oxide ions of the positive electrode layer attract lithium ions more easily than sulfide ions of the Solid electrolyte layer, a layer (depletion layer) insufficient in the amount of lithium ions is formed in the sulfide Solid electrolyte region close to the positive electrode layer, see Proceedings of the32nd Symposium on Solid states ions of Japan P130-131. The resistivity of the depletion layer region increases due to the lack of lithium ions, which decreases the discharge capacity of the lithium battery.
In order to solve the above problems, the prior art discloses such solutions: will consist of lithium ion conducting oxides (in Proceedings of the32nd Symposium on Solid Stateronics)of Japan P130-131 is LiNbO 3 ) The buffer layer is disposed on a surface of the positive electrode active material. The presence of such a lithium ion-conductive oxide layer restricts the migration of lithium ions and suppresses the formation of a depletion layer in the sulfide solid electrolyte layer, eventually suppressing a decrease in the discharge capacity of the lithium battery, i.e., suppressing deterioration in the output characteristics.
However, although it is reported in the prior art documents and patents that the harmful reaction between the positive electrode layer and the solid electrolyte layer can be effectively reduced by providing a buffer layer such as lithium niobate, lithium tantalate, etc., there are generally problems of high preparation cost and complicated preparation process, thus limiting its large-scale application in lithium batteries.
Disclosure of Invention
Therefore, an object of the present invention is to provide a lithium battery having a buffer layer and a method for preparing the same, in which the buffer layer is introduced to stabilize the interface between an electrolyte and a positive electrode, thereby improving the safety and lifespan of the lithium battery.
The invention provides a lithium battery with a buffer layer, wherein the buffer layer comprises a barrier buffer layer and/or a cladding buffer layer, wherein the barrier buffer layer is a coating layer positioned between a positive electrode and an electrolyte of the lithium battery; the coated buffer layer is a coating layer coated on the surface of the positive active material particles and/or the solid electrolyte particles, wherein the buffer layer is composed of a proton conductor containing hydrogen elements, and the chemical formula of the proton conductor containing the hydrogen elements is as follows: AH (advanced Shell preparation) x P y O 1/2+x/2+5y/2 Wherein x is more than 0 and less than or equal to 2, y is more than or equal to 0.8 and less than or equal to 2, A is one or more of Li, na, K, rb and Cs.
According to the lithium battery provided by the invention, the thickness of the barrier buffer layer can be 10nm to 1 μm, and is preferably 20nm to 500nm. The thickness of the clad buffer layer may be 0.1nm to 50nm, preferably 1nm to 25nm. The barrier buffer layer of the present invention has some lithium ion conductivity, however the lithium ion conductivity of the buffer layer is lower than the lithium ion conductivity of the electrolyte. Therefore, a thickness of the barrier buffer layer exceeding 1 μm is not preferable because too thick a buffer layer may hinder the migration of lithium ions. From this viewpoint, the thickness of the barrier buffer layer is further preferably less than or equal to 500nm. On the other hand, an excessively small thickness of the barrier buffer layer reduces the effect of suppressing the uneven distribution of charges in the solid electrolyte layer. Therefore, the thickness of the barrier buffer layer is preferably 10nm or more. In addition, the buffer layer of the present invention may be a coated buffer layer of 0.1nm to 50nm in thickness uniformly or non-uniformly coated on the surface of the positive electrode active material particles or the solid electrolyte particles.
According to the lithium battery provided by the invention, preferably, the proton conductor containing the hydrogen element is selected from LiH 2 PO 4 、Li 2 HPO 4 、LiHPO 3.5 、LiH 2 PO 3 、NaH 2 PO 4 、Na 2 HPO 4 、NaHPO 3.5 、NaH 2 PO 3 、KH 2 PO 4 、K 2 HPO 4 、KHPO 3.5 、KH 2 PO 3 、RbH 2 PO 4 、Rb 2 HPO 4 、RbHPO 3.5 And RbH 2 PO 3 One or more of (a).
The buffer layer can be characterized by a characterization method commonly used in the field, and the proton conductor AH containing hydrogen in the buffer layer can be characterized by characterization methods such as neutron diffraction spectrum, X-ray diffraction spectrum, raman spectrum, infrared spectrum, nuclear magnetic resonance spectrum and the like x P y O 1/2+x/2+5y/2 See Crystal Structure of LiH 2 PO 4 Studied by Single-Crystal Neutron Diffraction.Journal of the Physical Society of Japan79,(2010)；Crystal growth and morphology of LiH 2 PO 4 .Materials Chemistry and Physics 136,802-808(2012)；Kinetic process of dehydration at fusion temperature and the high-temperature phase transition in KH 2 PO 4 ,Journal of Molecular Structure 1034,112-118(2013)；Surface tension,viscosity,apparent molal volume,activation viscous flow energy and entropic changes of water+alkali metal phosphates at T＝(298.15,303.15,308.15)K，Journal of Molecular Liquids 203,29-38 (2015), and the like.
In one embodiment of the present invention, the lithium battery is an all-solid-state lithium battery including a positive electrode layer, a negative electrode layer, and an electrolyte layer containing solid electrolyte particles.
The positive electrode active material contained in the positive electrode is not particularly limited in the present invention. The particle diameter of the positive electrode active material particles may be 0.1 to 30 μm, preferably 1 to 10 μm.
Preferably, the positive electrode comprises a material represented by the general formula Li x M y O z The positive electrode active material is characterized in that M is a transition metal element, x is more than or equal to 0.02 and less than or equal to 2.2, y is more than or equal to 1 and less than or equal to 2, and z is more than or equal to 1.4 and less than or equal to 4. In the formula, M is preferably one or more of Co, mn, ni, al, ti, ta, nb, V, fe, and Si, more preferably one or more of Co, ni, and Mn. In some embodiments of the present invention, specific examples of the positive electrode active material may include: liCoO 2 、LiMnO 2 、LiNiO 2 、LiVO 2 、LiNi 1/3 Co 1/ 3 Mn 1/3 O 2 、LiMn 2 O 4 、Li(Ni 0.5 Mn 1.5 )O 4 、Li 2 FeSiO 4 、Li 2 MnSiO 4 And the like. In addition, except for the general formula Li x M y O z Examples of the positive electrode active material other than those shown include olivine-type positive electrode active materials such as LiFePO 4 And LiMnPO 4 And the like.
According to the lithium battery provided by the invention, the electrolyte can be a commonly used liquid electrolyte or solid electrolyte. The liquid electrolyte may be composed of an organic solvent and a lithium salt, and the organic solvent may be selected from one or more of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, ethylene sulfite, propylene sulfite, diethyl sulfite, gamma-butyrolactone, dimethyl sulfoxide, ethyl acetate, methyl acetate, tetrahydrofuran, dimethyl methane, 2-dimethyl tetrahydrofuran, 1, 2-dimethyl ethane, 1, 3-dioxolane, and diglymeSeed; the lithium salt may be selected from one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bistrifluoromethylsulphonylimide, lithium trifluoromethanesulfonate, lithium difluorooxalate borate, lithium bisoxalate borate. The solid electrolyte may be Li 3x La 2/3-x TiO 3 (x is more than or equal to 0 and less than or equal to 2/3); has the general formula Li x M y (PO 4 ) 3 (x is more than or equal to 1 and less than or equal to 3, y is more than or equal to 1 and less than or equal to 2, M is selected from one or more of Ge, al, ti, ga, zr, fe and Nb); a ceramic oxide having a garnet structure; has the composition of Li 2 S-P 2 S 5 And Li 2 S-Ge 2 S 5 The sulfide of (4); and solid electrolytes having other crystalline or amorphous structures, e.g. Li 3 N、LISICON(Lithium Super Ionic Conductor)、Thio-LISICON(Li 3.25 Ge 0.25 P 0.75 S 4 ) One or more of oxide-based, sulfide-based, phosphate-based and polymer-based materials such as LiPON, PEO, etc., wherein the ceramic oxide having a garnet structure such as oxide Li 5 La 3 M 2 O 12 (M = Nb or Ta), li 6 ALa 2 M 2 O 12 (A = Ca, sr or Ba; M = Nb or Ta), li 5.5 La 3 M 1.75 B 0.25 O 12 (M = Nb or Ta; B = In or Zr), li 7 La 3 Zr 2 O 12 And Li 7.06 M 3 Y 0.06 Zr 1.94 O 12 (M = La, nb, or Ta).
When a solid electrolyte is used, the solid electrolyte particles may have a particle size of 0.1 to 20 μm, preferably 0.5 to 10 μm.
According to the present invention, there is provided a lithium battery in which the negative electrode contains an active material that can occlude and release lithium ions, such as graphite, li metal, a metal capable of forming an alloy with Li metal, and a mixture thereof or an alloy thereof. As the metal capable of forming an alloy with Li (or referred to as "alloying material"), one or more of aluminum, silicon, tin, bismuth, and indium are preferable.
The invention also provides a preparation method of the lithium battery with the buffer layer, which comprises the following steps:
coating a solution of a proton conductor containing hydrogen element on the surface of a positive electrode and/or the surface of a solid electrolyte of a lithium battery, and drying to form a barrier buffer layer; the lithium battery is then assembled with the barrier buffer layer between the positive electrode and the electrolyte, and/or
Coating a proton conductor containing hydrogen on the surface of the positive electrode active material particles and/or the solid electrolyte particles to form a coating layer, preparing a positive electrode or a solid electrolyte by using the positive electrode active material particles and/or the solid electrolyte particles with the coating layer,
wherein the chemical formula of the proton conductor containing the hydrogen element is as follows: AH of x P y O 1/2+x/2+5y/2 Wherein x is more than 0 and less than or equal to 2, y is more than or equal to 0.8 and less than or equal to 2, A is one or more of Li, na, K, rb and Cs.
According to the production method provided by the present invention, the solution of the proton conductor containing a hydrogen element is preferably an aqueous solution. The concentration of the hydrogen-containing proton conductor solution is not particularly limited in the present invention, as long as the solution can be applied to the positive electrode surface and/or the solid electrolyte surface of a lithium battery to form a coating layer.
When the buffer layer is a coating layer arranged on the surface of the positive electrode active material particles and/or the solid electrolyte particles, the positive electrode active material particles or the electrolyte particles are mixed with the proton conductor containing the hydrogen element in the process of manufacturing the positive electrode and/or the electrolyte, and the mixture is heated at the temperature of 100-200 ℃ to form the coating layer; the hydrogen-containing proton conductor may be directly added to the organic solvent used for preparing the slurry when the positive electrode slurry is prepared.
In addition to the substrate, the positive electrode current collector layer, the positive electrode layer, the electrolyte layer (electrolyte and separator if liquid electrolyte), the negative electrode layer, and the negative electrode current collector layer, the lithium battery of the present invention further includes a barrier buffer layer disposed between the positive electrode layer and the electrolyte layer (or electrolyte), and/or a coating buffer layer coated on the surface of the positive electrode active material particles and/or the solid electrolyte particles. Three representative structures of lithium batteries of the invention are described in detail below as examples:
1. all-solid-state lithium battery with barrier buffer layer
Fig. 1 is a longitudinal sectional view of an all solid-state lithium battery having a barrier buffer layer according to the present invention. The lithium battery 1 includes: a positive electrode current collector layer 11, a positive electrode layer 13, a buffer layer 16, an electrolyte layer (EL layer) 15, a negative electrode layer 14, and a negative electrode current collector layer 12 laminated in this order between the substrates 10 and 17.
2. All-solid-state lithium battery with cladding buffer layer
Fig. 2 is a longitudinal sectional view of an all solid-state lithium battery having a clad buffer layer according to the present invention. The lithium battery 2 includes: and a positive electrode collector layer 21, a negative electrode collector layer 22, a positive electrode layer 23, a negative electrode layer 24, and an EL layer 25 disposed between the substrates 20 and 27 having insulating properties, wherein the EL layer 25 includes electrolyte particles 28 and a coating buffer layer 26 coated on the surfaces of the electrolyte particles 28.
3. Liquid electrolyte lithium battery with barrier buffer layer
Fig. 3 is a longitudinal sectional view of a liquid electrolyte lithium battery having a barrier buffer layer. The lithium battery 3 includes: and a positive electrode current collector layer 31, a negative electrode current collector layer 32, a positive electrode layer 33, a negative electrode layer 34, an electrolyte 35, a buffer layer 36 and a separator layer 39 which are arranged between the substrates 30 and 37 having insulating properties, wherein the positive electrode layer 33 comprises positive electrode active material particles 38 and a coated buffer layer 36 coated on the surfaces of the positive electrode active material particles 38.
The constituent elements of a typical lithium battery according to the present invention will be described in detail below.
< substrate >
The substrate is an insulating member configured to support the layers of the lithium battery. The substrate may be formed of, for example, polyphenylene sulfide (PPS) or the like. Alternatively, the substrate may be formed of, for example, srTiO 3 MgO or SiO 2 Such as ceramic material. When the substrate is formed of ceramic, the layers forming the lithium battery using a vapor deposition method or the like are not likely to cause thermal damage to the substrate. It should be noted that the substrate may be omitted depending on the structure of the lithium battery. For example, when the battery has a structure in which the laminate body is contained in a pouch case, then the substrate is not particularly necessary. The positive electrode collector, which will be described later, may also function as a substrate.
< Positive electrode Current collector layer >
The positive electrode current collector layer is a metal film having a predetermined thickness. The positive electrode current collector layer is preferably formed of one of aluminum, nickel alloys thereof, and stainless steel. The current collector composed of a metal film may be formed by a physical vapor deposition method (PVD method) or a chemical vapor deposition method (CVD method). In particular, when the metal film current collector is formed to have a predetermined pattern, the current collector having the predetermined pattern can be easily formed by using an appropriate mask. Alternatively, the positive electrode current collector layer may be formed by bonding a metal foil to an insulating substrate under pressure.
< Positive electrode layer >
The positive electrode layer preferably contains a compound represented by the general formula Li x M y O z The positive electrode active material is represented by the formula (I), wherein M is a transition metal element, x is 0.02-2.2, y is 1-2, z is 1.4-4, M is preferably one or more of Co, mn, ni, al, ti, ta, nb, V, fe and Si, and more preferably one or more of Co, ni and Mn. Specific examples of the positive electrode active material include: liCoO 2 、LiMnO 2 、LiNiO 2 、LiVO 2 、LiNi 1/3 Co 1/3 Mn 1/3 O 2 、LiMn 2 O 4 、Li(Ni 0.5 Mn 1.5 )O 4 、Li 2 FeSiO 4 、Li 2 MnSiO 4 And so on. In addition, except for the general formula Li x M y O z Examples of the positive electrode active material other than those shown include olivine-type positive electrode active materials such as LiFePO 4 And LiMnPO 4 And the like.
The positive electrode layer may further contain a conductive auxiliary. Examples of the conductive aid include carbon black (such as acetylene black), natural graphite, thermally expanded graphite, carbon fiber, ruthenium oxide, titanium oxide, and metal fiber made of aluminum, nickel, or the like. In particular, carbon black is preferable because a small amount of carbon black is added to ensure high conductivity.
As a method of forming the positive electrode layer, a wet method such as a coating method or a screen printing method can be employed. When the positive electrode layer is formed by such a wet process, the positive electrode layer may contain a binder such as polytetrafluoroethylene or polyvinylidene fluoride. The positive electrode layer may also be formed by a dry process such as a deposition method, an ion plating method, a sputtering method, or a laser ablation method.
< negative electrode current collector layer >
The negative current collector layer is a metal film present on the negative electrode layer. The negative current collector layer is preferably formed of one metal of copper, nickel, iron, chromium, and alloys thereof. The negative current collector layer may be formed by PVD or CVD.
< negative electrode layer >
The negative electrode layer is composed of a layer containing an active material that can occlude and release lithium ions. For example, as the negative electrode layer, one selected from graphite, li metal, a metal capable of forming an alloy with Li metal, a mixture thereof, or an alloy thereof can be preferably used. As the metal capable of forming an alloy with Li ("alloying material"), at least one of aluminum, silicon, tin, bismuth, and indium is preferable. The negative electrode layer containing the above-described elements is preferable because the negative electrode layer can function as a current collector and has a high ability to store and release lithium ions.
The negative electrode layer described above may be preferably formed by a coating method or a vapor deposition method. The negative electrode layer is preferably formed by: a metal foil is placed on the EL layer, and the metal foil and the EL layer are bonded together by pressing or an electrochemical method.
< EL layer >
The EL layer is an electrolyte layer. The electrolyte material is not particularly limited as long as it has Li ion conductivity, and the electrolyte layer includes a liquid electrolyte that is commonly used at present and a solid electrolyte that is reported at present. Among them, the all solid-state lithium battery having the barrier buffer layer preferably employs a sulfide solid electrolyte material. This is because the sulfide solid electrolyte material is more reactive than the oxide solid electrolyte material, and therefore easily reacts with the positive electrode active material, and a high resistance layer is easily formed between the sulfide solid electrolyte material and the positive electrode active material.
In addition, in the present invention, by coating the positive electrode active material particles or the electrolyte particles with the proton conductor containing a hydrogen element, an increase in the interface resistance between the positive electrode active material and the sulfide solid electrolyte material can be effectively suppressed.
As a method for forming the EL layer, a solid phase method or a vapor deposition method can be employed. For example, the solid phase method may include: preparing a raw powder using mechanical milling, and then sintering the raw powder to form the EL layer; the vapor deposition method may include a PVD method and a CVD method. Specific examples of the PVD method include a vacuum evaporation method, a sputtering method, an ion plating method, and a laser ablation method. Specific examples of the CVD method include a thermal CVD method and a plasma CVD method. In the case where the EL layer is formed by vapor deposition, the thickness of the EL layer can be reduced as compared with the case where the EL layer is formed by the solid phase method.
< buffer layer >
The buffer layer is a layer that prevents a side reaction of the EL layer 15 with the positive electrode layer 13 to suppress uneven distribution of electric charges at the interface between the EL layer and the positive electrode layer, thereby suppressing formation of a depletion layer in a region of the EL layer near the interface.
The buffer layer may be a barrier buffer layer, a cladding buffer layer, or both. The buffer layer is formed of the proton conductor containing the hydrogen element.
In the all-solid-state lithium battery having the barrier buffer layer, by merely forming a coating layer of the proton conductor containing the hydrogen element on the surface of the positive electrode layer or the surface of the EL layer between the positive electrode layer and the EL layer, it is possible to suppress uneven distribution of lithium ions from the EL layer to the positive electrode layer and to suppress formation of a depletion layer in the EL layer. Therefore, the lithium battery can be prepared very simply and efficiently. In addition, since the active material contained in the positive electrode layer can be freely selected, a lithium battery can be prepared according to the use of the lithium battery.
In the all-solid-state lithium battery with the coated buffer layer, the buffer layer covers the surface of solid electrolyte particles, so that the stability of the solid electrolyte, especially sulfide, is favorably improved, and the buffer layer isolates moisture in the air and reduces the sensitivity of the solid-state battery to the environment in the production process; or the buffer layer covers the surface of the positive active material particles, so that the surface oxidizability of the positive active material particles in a charging state is reduced, and the side reaction between the positive active material particles and the electrolyte is effectively prevented.
In the liquid electrolyte lithium battery with the cladding buffer layer, the buffer layer covers the surface of the positive electrode material particles, so that lithium ions can be conducted more quickly, the stability between the liquid electrolyte and the positive electrode material is promoted, and the buffer layer can slow down the mutual reaction between the positive electrode layer and the electrolyte.
Drawings
Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:
fig. 1 is a longitudinal sectional view of an all solid-state lithium battery having a barrier buffer layer according to the present invention;
fig. 2 is a longitudinal sectional view of an all solid-state lithium battery having a clad buffer layer according to the present invention;
fig. 3 is a longitudinal sectional view of a liquid electrolyte lithium battery having a barrier buffer layer;
FIG. 4 shows LiH prepared in example 3 of the present invention 2 PO 4 Coated LiCoO 2 TEM spectra of the particles;
FIG. 5 shows LiH prepared in example 6 of the present invention 2 PO 4 Coated LiNi 0.5 Mn 1.5 O 4 Raman spectrum of the particle (750-1250 cm) -1 )；
FIG. 6 shows LiH prepared in example 6 of the present invention 2 PO 4 Coated LiNi 0.5 Mn 1.5 O 4 Raman spectrum of the particles (1400-4000 cm) -1 )。
Detailed Description
The present invention is described in further detail below with reference to specific embodiments, which are given for the purpose of illustration only and are not intended to limit the scope of the invention.
A button cell type lithium battery (example 1) having the structure shown in fig. 1 and a button cell type lithium battery (comparative example 1) as a comparative example, a button cell type lithium battery (example 2) having the structure shown in fig. 2, and button cell type lithium batteries (examples 3, 4 and 5) having the structure shown in fig. 3 and button cell type lithium batteries (comparative examples 2 and 3) as comparative examples were prepared. In these lithium batteries, the positive electrode current collector layer also functions as a substrate, and thus the substrate shown in the drawings can be omitted.
Example 1
Preparing a button cell type lithium battery having a structure as shown in FIG. 1 by reacting LiCoO 2 Used as a positive electrode active material. The lithium battery comprises the following materials in all layers and the following thicknesses:
wherein, adopt spin-coating method to form separation buffer layer: and (3) coating 50wt.% of lithium dihydrogen phosphate aqueous solution on the surface of the positive layer in a spinning way, then putting the positive layer into a vacuum oven at 55 ℃ for drying, and measuring the thickness of the barrier buffer layer by using a secondary particle texture analyzer to be 5nm.
Comparative example 1
A lithium battery was fabricated in the same manner as in example 1, except that the lithium battery did not include a buffer layer. The materials of each layer and the thickness of each layer are as follows:
example 2
Preparing a button cell type lithium battery having a structure as shown in FIG. 2 by reacting LiCoO 2 Used as a positive electrode active material. Each layer of the lithium battery material and each layerThe thicknesses were as follows:
the method for forming the cladding buffer layer comprises the following steps: mixing the solid electrolyte particles with lithium dihydrogen phosphate in a mass ratio of 20.
Example 3
Preparing a button cell type lithium battery having a structure shown in FIG. 3, liCoO 2 Used as a positive electrode active material. The lithium battery comprises the following materials of each layer and the thickness of each layer:
the method for forming the cladding buffer layer comprises the following steps: subjecting LiCoO to condensation 2 And LiH 2 PO 4 Mixing the components in a mass ratio of 20 2 And (3) particles.
FIG. 4 shows LiH produced in this example 2 PO 4 Coated LiCoO 2 TEM pattern of the particles, the thickness of the buffer layer was found to be 6nm.
Example 4
Preparing a button cell type lithium battery having a structure shown in FIG. 3 by reacting LiCoO 2 Used as a positive electrode active material. The lithium battery comprises the following materials in all layers and the following thicknesses:
the method for forming the cladding buffer layer comprises the following steps: subjecting LiCoO to condensation 2 With KH 2 PO 4 Mixing the components in a mass ratio of 20 2 And (3) granules.
Comparative example 2
A lithium battery was fabricated in the same manner as in examples 3 and 4, except that the lithium battery did not include a buffer layer. The materials of each layer and the thickness of each layer are as follows:
example 5
Preparing a button cell type lithium battery having a structure shown in FIG. 3, and mixing LiMn 2 O 4 Used as a positive electrode active material. The lithium battery comprises the following materials in all layers and the following thicknesses:
the method for forming the cladding buffer layer comprises the following steps: mixing LiMn 2 O 4 With Na 2 HPO 4 Mixing the components in a mass ratio of 20 2 HPO 4 Buffer layer coated LiMn 2 O 4 And (3) granules.
Example 6
A button cell type lithium battery having a structure shown in FIG. 3 was prepared by charging LiNi 0.5 Mn 1.5 O 4 Used as a positive electrode active material. Each layer of the lithium battery is made ofAnd the thickness of each layer is as follows:
the method for forming the cladding buffer layer comprises the following steps: reacting LiNi 0.5 Mn 1.5 O 4 And LiH 2 PO 4 Mixing the components in a mass ratio of 20 2 PO 4 Buffer layer-coated LiNi 0.5 Mn 1.5 O 4 And (3) granules.
Comparative example 3
A lithium battery was fabricated in the same manner as in examples 3 and 4, except that the lithium battery did not include a buffer layer. The materials of each layer and the thickness of each layer are as follows:
performance testing
For the lithium batteries prepared in examples 1 and 2 and comparative example 1, the current density was 0.05mA/cm 2 After charging at a cut-off voltage of 4.2V, the internal resistance was measured by a complex impedance method, and the test results are summarized in table 1.
TABLE 1
| Reaction resistance (omega cm) 2 ) | |
| Example 1 | 52 |
| Comparative example 1 | 386 |
| Example 2 | 105 |
As can be seen from the comparison of data in table 1, the buffer layer of the lithium battery including the buffer layer according to the present invention effectively protects the interface between the positive electrode and the solid electrolyte layer, and reduces the internal resistance of the lithium battery, as compared to a battery without the buffer layer.
The lithium batteries prepared in examples 3 to 5 and comparative examples 2 to 3 were allowed to stand at room temperature (25 ℃) for 10 hours, and then charge and discharge activation was performed on the button cells, followed by charge and discharge cycle testing of the button cells prepared above using a blue cell charge and discharge tester. Cycling at 25 deg.C and 55 deg.C for 1 week at 0.1C, and then continuing cycling at 0.2C for 200 weeks while controlling the charging and discharging voltage of the battery to be 3.5V-4.9V.
The capacity after cycling, capacity Retention (CR), and average coulombic efficiency (ACR) results are summarized in tables 2 and 3.
TABLE 2
TABLE 3
As can be seen from the data in tables 2 and 3, the LiH will be measured 2 PO 4 、KH 2 PO 4 Or Na 2 HPO 4 The lithium battery made of the coated positive active material particles has better cycle stability and cycle efficiency than the lithium battery made of the uncoated positive active material particlesThe improvement shows that the proton conductor containing the hydrogen element has obvious protective effect on the surface of the positive active material particles.
As can be seen from FIG. 4, the LiH passes through 2 PO 4 LiCoO after coating 2 The surface of the particles is uniformly covered with a coating layer with the thickness of about 6nm.
As can be seen from FIG. 5, the LiH is passed through 2 PO 4 Coated LiNi 0.5 Mn 1.5 O 4 Raman spectra of the particles were 892, 928 and 1053cm -1 All show PO 4 The peak of vibration of (1). From FIG. 6 it can be seen that the LiH passes through 2 PO 4 Coated LiNi 0.5 Mn 1.5 O 4 The Raman spectra of the particles were 1650, 2312, 2770 and 3080cm -1 All showed O — H vibrational peaks. Fig. 5 and 6 characterize the presence of the buffer layer from a raman spectroscopy perspective and provide a means for determining whether a cladding layer as described herein is present. The similar characterization means also comprises neutron diffraction spectrum, X-ray diffraction spectrum, infrared spectrum, nuclear magnetic resonance spectrum and the like.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The lithium solid-state battery of the present invention as used herein may be either a primary battery or a secondary battery, of which the secondary battery is preferable, unless explicitly stated or apparent from the context. This is because charge and discharge can be repeated, and is useful as a vehicle-mounted battery, for example. Examples of the shape of the all solid-state lithium battery of the present invention include a coin shape, a laminate shape, a cylindrical shape, and a square shape. The method for producing the all-solid-state lithium battery of the present invention is not particularly limited as long as the above-described all-solid-state lithium battery can be obtained, and the same method as that for producing a general all-solid-state lithium battery can be used.
The present invention is not limited to the above embodiments, and the above embodiments may be appropriately modified without departing from the spirit and scope of the present invention. For example, as for the arrangement of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer constituting the lithium battery, those different from those described in the above embodiments may be used: in these different arrangements (non-laminated structures), the positive-electrode layer and the negative-electrode layer do not overlap with each other when the battery is viewed from above. Regardless of the structure selected, a buffer layer should be provided between the positive electrode layer and the electrolyte layer so that the positive electrode layer and the electrolyte layer are not in direct contact with each other.
The above embodiments are illustrative, and any embodiments having substantially the same configuration as the technical idea described in the scope of the claims of the present invention and having the same operational effects are included in the technical scope of the present invention.
Claims (9)
1. An all-solid-state lithium battery having a buffer layer, the all-solid-state lithium battery comprising a positive electrode layer, a negative electrode layer, and an electrolyte layer, the electrolyte layer containing sulfide solid electrolyte particles, the buffer layer comprising a barrier buffer layer or a clad buffer layer, wherein the barrier buffer layer is a coating layer between the positive electrode layer and the electrolyte layer of the lithium battery; the coated buffer layer is coated on the surface of the solid electrolyte particle, wherein the buffer layer is composed of a proton conductor containing hydrogen elements, and the chemical formula of the proton conductor containing hydrogen elements is as follows: AH (advanced Shell preparation) x P y O 1/2+x/2+5y/2 Wherein x is more than 0 and less than or equal to 2, y is more than or equal to 0.8 and less than or equal to 2, and A is one or more of Li, na, K, rb and Cs.
2. The lithium battery of claim 1, wherein the clad buffer layer has a thickness of 0.1nm to 50 nm.
3. The lithium battery of claim 1, wherein the clad buffer layer has a thickness of 1nm to 25nm.
4. The lithium battery of claim 1 wherein the hydrogen containing proton conductor is selected from LiH 2 PO 4 、Li 2 HPO 4 、LiHPO 3.5 、LiH 2 PO 3 、NaH 2 PO 4 、Na 2 HPO 4 、NaHPO 3.5 、NaH 2 PO 3 、KH 2 PO 4 、K 2 HPO 4 、KHPO 3.5 、KH 2 PO 3 、RbH 2 PO 4 、Rb 2 HPO 4 、RbHPO 3.5 And RbH 2 PO 3 One or more of (a).
5. The lithium battery according to claim 1, wherein the solid electrolyte particles have a particle size of 0.1 to 30 μm.
6. The lithium battery according to claim 5, wherein the solid electrolyte particles have a particle size of 0.2 to 10 μm.
7. A method of manufacturing a lithium battery having a buffer layer as claimed in any one of claims 1 to 6, the method comprising:
coating a solution of a proton conductor containing hydrogen elements on the surface of a positive electrode layer and/or the surface of an electrolyte layer of a lithium battery, and drying to form a barrier buffer layer; then assembling the lithium battery in such a manner that the barrier buffer layer is located between the positive electrode layer and the electrolyte layer, or
Coating a proton conductor containing hydrogen element on the surface of solid electrolyte particles to form a coating buffer layer, preparing a solid electrolyte by using the solid electrolyte particles with the coating buffer layer,
wherein the chemical formula of the proton conductor containing the hydrogen element is as follows: AH of x P y O 1/2+x/2+5y/2 Wherein x is more than 0 and less than or equal to 2, y is more than or equal to 0.8 and less than or equal to 2, and A is one or more of Li, na, K, rb and Cs.
8. The production method according to claim 7, wherein the solution of the proton conductor containing the hydrogen element is an aqueous solution.
9. The production method according to claim 7, wherein the production method comprises: the electrolyte particles are mixed with the proton conductor containing the hydrogen element, and the mixture is heated at the temperature of 100 to 300 ℃ to form a coating buffer layer.
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