CN115189012A - Solid-state battery cell with inter-embedded structure and preparation method thereof - Google Patents

Abstract

The invention provides a solid-state battery cell with a mutual embedded structure, which comprises a positive electrode, a negative electrode and a solid-state electrolyte layer, wherein the positive electrode comprises a positive electrode current collector and a positive electrode material loaded on the positive electrode current collector, and the surface of the positive electrode material is provided with at least one pit; the solid electrolyte layer is attached to the entire surface of the pit; the negative electrode comprises at least one negative electrode area and a negative electrode current collector electrically connected with the negative electrode area, wherein the negative electrode area is formed by a negative electrode material filled with pits attached with the solid electrolyte layer, and the negative electrode current collector is arranged on the surface of the negative electrode area and is electrically connected with the negative electrode area. The invention also provides a preparation method of the solid-state battery cell with the mutually embedded structure. The invention also provides a solid-state battery cell with a series structure, which is formed by connecting at least two battery cell units in series through the connecting terminal. The solid-state battery cell has the characteristics of large contact area between the electrode and the solid electrolyte and difficult short circuit.

Description

Solid-state battery cell with inter-embedded structure and preparation method thereof

technical field

The invention belongs to the technical field of energy storage. Specifically, the present invention relates to a solid-state battery cell with an inter-embedded structure and a preparation method thereof.

Background technique

Solid-state batteries are widely regarded as the next-generation battery technology due to their high safety and high specific energy characteristics. Since the solid electrolyte in the solid-state battery replaces the lithium-ion battery electrolyte, the positive electrode material and the electrolyte are connected by a solid-solid interface. When using positive and negative electrode materials with high volume effect, the low solid-solid interface contact area and interface separation directly affect the electrical performance of the battery.

At the same time, due to the dense crimping process of the battery during the assembly process, the infiltration process is easy to occur at the solid-solid interface, resulting in the deformation of low Young's modulus materials such as electrolytes. In a simple parallel-structure solid-state battery, this large-planar ultra-thin electrolyte layer structure can easily form an internal short circuit in the battery.

At present, there is an urgent need for a cell structure that has a large contact area between the electrode and the solid electrolyte, is not easily short-circuited inside the battery, and can be freely combined in series and parallel.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a solid-state battery cell with an inter-embedded structure, which can overcome the problem of insufficient contact area between electrodes and solid-state electrolyte caused by the parallel structure in the current solid-state battery packaging, and can also overcome the electrode volume effect after cycling. cause structural damage. The solid-state battery cell provided by the invention divides the cell into a huge number of tiny cells, can eliminate a small number of defective cells during manufacture, and can be freely combined in series and parallel according to the design voltage requirements. Another object of the present invention is to provide a method for preparing a solid-state battery cell with an inter-embedded structure.

The above objects of the present invention are achieved through the following technical solutions.

In a first aspect, the present invention provides a solid-state battery cell with an inter-embedded structure, which includes a positive electrode, a negative electrode, and a solid-state electrolyte layer, wherein,

The positive electrode comprises a positive electrode current collector and a positive electrode material supported on the positive electrode current collector, wherein the surface of the positive electrode material has at least one pit;

the solid electrolyte layer is attached to the entire surface of the pit

The negative electrode includes at least one negative electrode region and a negative electrode current collector electrically connected to the negative electrode region, wherein the negative electrode region is formed of a negative electrode material filled with a pit with a solid electrolyte layer attached thereto, and the negative electrode current collector is arranged on the negative electrode material. on the surface of the negative electrode region and form an electrical connection with the negative electrode region.

Preferably, in the solid-state battery cell with the inter-embedded structure of the present invention, an electrical insulating material layer is provided on the surface of the positive electrode material, so as to electrically insulate the positive electrode material from the negative electrode current collector. In the present invention, the electrically insulating material layer provided on the surface of the positive electrode material means that the electrical insulating material layer covers the surface of the positive electrode material or covers and extends beyond the surface of the positive electrode material.

Preferably, in the solid-state battery cell with an inter-embedded structure according to the present invention, the electrical insulating material layer has through holes at positions corresponding to the negative electrode regions, and the negative electrode current collector has through holes corresponding to the negative electrode regions. The holes are matched with the protrusions to penetrate the electrically insulating material layer to be electrically connected to the negative electrode region.

Preferably, in the solid-state battery cell with the inter-embedded structure according to the present invention, the shape of the pit is cylindrical, pyramidal, frustoconical or prismatic.

In a specific embodiment of the present invention, the shape of the recess is an inverted frustoconical shape.

Preferably, in the solid-state battery cell with an inter-embedded structure according to the present invention, the pits are arranged in an array.

Preferably, in the solid-state battery cells with an inter-embedded structure according to the present invention, the array arrangement is performed in the following manner:

The dimples are arranged in separate rows along a first direction and spaced within each row in a second direction, wherein the first and second directions are perpendicular to each other and constitute The plane is parallel to the upper surface of the positive electrode material.

Preferably, in the solid-state battery cell with the inter-embedded structure of the present invention, the size of the pit is 100-20000 μm, preferably 100-9000 μm.

Preferably, in the solid-state battery cell with an inter-embedded structure according to the present invention, the thickness of the solid-state electrolyte layer is 1-100 μm.

Preferably, in the solid-state battery cell with the inter-embedded structure of the present invention, the thickness of the negative electrode current collector is 1-50 μm, preferably 1-20 μm.

In a second aspect, the present invention provides a method for preparing a solid-state battery cell with an inter-embedded structure of the present invention, which comprises the following steps:

(1) Load the positive electrode material on the surface of the positive electrode current collector, and form at least one pit on the surface of the positive electrode material by pressing;

(2) attaching a solid electrolyte layer to the entire surface of the pit;

(3) filling the pits with the solid electrolyte layer attached with the negative electrode material to form the negative electrode region;

(4) electrically connecting the negative electrode current collector with the negative electrode region;

(5) Optionally, before the step (4), an electrical insulating material layer is formed on the surface of the positive electrode material.

In a third aspect, the present invention provides a solid-state battery cell with a series structure, which is composed of at least two cell subunits connected in series through connecting terminals (see FIG. 3 ), and the cell subunits include the Structure of solid-state battery cells.

In a specific embodiment of the present invention, the negative electrode current collector can be layered on the top to form a single-layer cell structure, and can also be compatible with lamination to realize that each single-layer cell in a solid-state battery is connected in series with each other.

In a specific embodiment of the present invention, a solid-state battery cell is encapsulated by using an insulating water-blocking and oxygen-blocking film by hot pressing to form a solid-state battery.

In a specific embodiment of the present invention, before using the positive electrode current collector, it needs to be subjected to surface cleaning treatment.

In a specific embodiment of the present invention, the cathode material is loaded on the surface of the cathode current collector with the back structure, and an array of inverted frustoconical dimples is prepared by cold pressing.

In particular embodiments of the present invention, the liquid phase electrolyte is attached to the dimples through masks corresponding to the inverted frustoconical dimples, or the electrolyte is attached to the dimples by deposition. The electrolyte is then shaped and heat treated using a mold to form the desired solid state electrolyte.

In a specific embodiment of the present invention, the negative electrode slurry is filled inside the inverted frustoconical solid electrolyte interface, and the negative electrode slurry is injected by cold rolling or melting method to form the negative electrode material, and the interface between the electrolyte and the negative electrode material can be made of or Without treatment, it is preferable to use a metal mixed conductive layer for modification.

In a specific embodiment of the present invention, conventional methods in the art can be used to prepare the desired negative electrode current collector of the present invention, for example, refer to the method disclosed in patent application 201410440238.6.

In a specific embodiment of the present invention, the negative electrode current collector is drawn out by cold pressing, and the single-layer battery cells are stacked into groups to realize the stacking in the battery, and then realize the series connection in the battery.

In a specific embodiment of the present invention, the positive and negative electrode tabs are drawn out from the side of the battery cell, and then transferred and thermally sealed.

The present invention has the following beneficial effects:

On the one hand, the solid-state battery cell of the present invention has the characteristics of a large contact area between the electrode and the solid-state electrolyte. On the other hand, the solid-state battery cell of the present invention is not easily short-circuited, and can also overcome the problem of structural damage caused by the electrode volume effect after cycling. In addition, the solid-state battery cell provided by the present invention divides the cell into a huge number of tiny cells, which can eliminate a small number of defective cells during manufacture. The series connection between each cell sub-unit is realized (see Figure 3). The solid-state battery cell with the inter-embedded structure provided by the present invention is actually a parallel connection between the cell structures (see FIG. 1 ). It can be seen that the free series-parallel connection of the cell structures can be realized by the solid-state battery cells with the inter-embedded structure provided by the present invention.

Description of drawings

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein:

1 is a side cross-sectional view of a solid-state battery cell according to a specific embodiment of the present invention;

2 is a top cross-sectional view of a solid-state battery cell without a negative electrode current collector according to a specific embodiment of the present invention;

3 is a side cross-sectional view of a series of cell subunits according to a specific embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the specific embodiments, and the given examples are only for illustrating the present invention, rather than for limiting the scope of the present invention.

Example 1

(1) Preparation of positive electrode

An aluminum foil with a thickness of 12 μm was used as the positive electrode current collector, then deionized water and ethanol were used to sonicate the positive electrode current collector for 30 min, respectively, and then the positive electrode current collector was dried at 120 °C in a vacuum environment. The mixture of LCO cathode active material: LGPS sulfide electrolyte: carbon nanotube: PVDF mass ratio of 5:3:1:1 was ball-milled at a speed of 400 r/min for 3 h in an inert _N2 atmosphere, and then dispersed into anhydrous NMP. , to form a mixed solution with a solid content of 60 wt %. By coating the mixed solution on one surface of the positive electrode current collector, a positive electrode precursor with a thickness of 1800 μm is formed, and the positive electrode precursor is compacted with a circular frustum-shaped metal abrasive tool with a depth of 1250 μm in a low vacuum <100Pa environment to form the positive electrode precursor, It was then cold rolled using a pressure of 50 MPa for 15 min to form the desired positive electrode.

(2) Preparation of solid electrolyte layer

LGPS and LPS sulfide solid electrolyte (mixed in a 1:1 weight ratio) and PTFE binder were ball-milled and mixed at a speed of 300 r/min under _N2 inert atmosphere for 2 h, wherein the PTFE binder accounted for 2 wt% of the total mixture. After mixing, the mixture was dispersed in anhydrous cyclohexane to form a mixed solution with a solid content of 80% by mass. A mask is covered on the surface of the positive electrode to shield the non-inverted frustoconical region, and the mixed solution is sprayed into the pit by spraying to form a liquid electrolyte with a thickness of 200 μm. Then, in a low vacuum <100Pa environment, the liquid electrolyte is compacted with a busbar coaxial frustum-shaped metal grinding tool to fit the inverted frustoconical pit of the positive electrode. Then cold-rolled at 10 MPa for 5 min, and then started to heat and press at 200 °C for 5 min to form a crystallized solid electrolyte layer structure.

(3) Preparation of negative electrode

A 1 μ gold coating was deposited on the solid-electrolyte interface using magnetron sputtering to form a mixed ionically conductive layer. The metal lithium was heated to 180 °C under an inert atmosphere of Ar ₂ for thermal melting, and the micro-needle was used to inject the metal lithium into the pores, and the filled negative electrode was flush with the platform structure of the positive electrode.

(4) Preparation of negative electrode current collector

A flexible anode bilayer current collector was formed using a 20 μm-thick composite flexible FPC film with a ring-shaped insulating layer and a Fe metal conductive layer. Then, the negative double-layer current collector was placed on top of the flat negative electrode, and cold-pressed with a pressure of 10 MPa for 5 min. Then, a polyimide film with a thickness of 30 μm with positive and negative electrode tabs is used, and cold-rolled with the positive and negative electrode current collectors respectively to complete the preparation of a single-piece solid-state battery cell.

(5) Preparation of solid-state batteries

Repeat the above-mentioned single-layer cell preparation steps, transfer the stack on the outside of the negative pole piece, and form a series connection in the cell. Use multiple layers of prepared cell layers to align and stack, weld positive and negative tabs on the edge of the cell, use aluminum-plastic film for pre-packaging (edge 150°C), and install the prepared solid-state battery cells in a vacuum. After being placed in a sealed bag, the solid-state battery was prepared after hot pressing at 600 MPa at 170 °C for 30 s with a hot isostatic press.

Comparative Example 1

(1) Preparation of positive electrode

The mixture of LCO ternary cathode material: LGPS sulfide electrolyte: Super P conductive carbon: PTFE: graphene mass ratio of 4.5: 3: 1.5: 0.5: 0.5 was ball-milled at a speed of 300 r/min in a N inert atmosphere for ₁ h after mixing. , dispersed into anhydrous cyclohexane to form a mixed solution with a solid content of 60% by mass. The mixed solution was coated on the surface of a common positive electrode current collector to form a positive electrode precursor with a thickness of 120 μm, and then vacuum-dried at 120° C. for 6 hours. The positive electrode precursor is compacted into a flat electrode with a flat abrasive in a low vacuum <100Pa environment. Then use 10MPa pressure for cold pressing for 5 minutes, then start heating and hot pressing at 150°C for 10 minutes, and continue to use isostatic press for 60s cold pressing at 400MPa, and then remove the pressure.

(2) Preparation of solid electrolyte layer

After mixing the LPS sulfide solid electrolyte with 2wt% PTFE binder, ball mill mixing at a speed of 300r/min under _N2 inert atmosphere for 1h, then, the mixture was dispersed in anhydrous cyclohexane to form 80% solid content mass ratio of the mixture. The mixed solution was sprayed onto the surface of the prepared flat cathode by spraying to form a liquid electrolyte with a thickness of 20 μm. Then, compaction was carried out in a low vacuum <100Pa environment, followed by cold rolling at 10MPa for 5min, and then heating and hot pressing at 160°C for 10min to form a solid electrolyte layer structure. Using nanosecond infrared laser drying to rapidly localize only the electrolyte area, elevating the electrolyte to 460°C increases the degree of crystal splendor.

(3) Preparation of negative electrode

Metal Li was mixed with 2wt% of Ag at 180°C to form liquid metal, which was then uniformly coated on the surface of the stainless steel substrate, and the negative electrode was separated after cooling. The metal lithium negative electrode was thinned to 100 μm using a roll press. A 30 nm high mixed conductivity amorphous carbon layer was deposited on the surface of metallic lithium with a thickness of 100 μm by ion source sputtering as a conductive layer. The prepared negative electrode mixed conductive layer is contacted with the prepared solid electrolyte layer to form a planar stack structure.

(4) Preparation of negative electrode current collector

Using a composite flexible FPC film with a thickness of 20 μm with a ring-shaped insulating layer and a Fe metal conductive layer, a flexible anode double-layer current collector was formed. Then, the negative double-layer current collector was placed on top of the flat negative electrode, and cold-pressed with a pressure of 10 MPa for 5 min. Then, a polyimide film with a thickness of 30 μm with positive and negative electrode tabs is used, and cold-rolled with the positive and negative electrode current collectors respectively, thereby completing the preparation of a single-piece solid-state battery cell.

(5) Preparation of solid-state batteries

The two prepared cell layers were aligned and superimposed, and the prepared solid-state battery cell film was placed in a polyimide film sealed bag, and then hot-pressed at 200°C for 30s at a pressure of 400MPa with a press. Then, a laser is used to remove the excess polyimide film outside the side tabs to form a solid-state battery.

Example 2

The electrochemical performances of the fabricated nested array-structured solid-state batteries and parallel-structured batteries were tested with the battery testing system of Wuhan Landian Electronics Co., Ltd. at a test temperature of 60 °C and a test voltage of 3.0–4.3 V vs Li ⁺ /Li, the test rates are 0.05C and 0.1C respectively, and the nominal capacity is calculated as 145mAh/g. The specific capacity of the entire battery is calculated by the mass of the LCO cathode active material.

Table 1 Performance test results of Example 1 and Comparative Example 1

It can be seen from Table 1 above that when the solid-state battery is prepared by the circular truncated array structure, the electrochemical performance is significantly improved due to the high contact area between the electrode and the solid-state electrolyte. First, the discharge capacity was higher at 0.05C and 0.1C; secondly, the cycle capacity retention at 0.1C rate for 50 cycles increased from about 70% to about 96%. The main reason for achieving this performance is that the contact area between the electrode and the solid electrolyte is greatly increased through the nested mode, which improves the capacity release. At the same time, the cavity-type structure alleviates the material failure caused by volume expansion, so the cycle stability is improved. The invention solves the problem of capacity attenuation caused by poor interface contact and large volume change in solid-state batteries, and has positive significance for practical applications.

Claims (10)

1. A solid-state battery cell having an inter-embedded structure includes a positive electrode, a negative electrode, and a solid-state electrolyte layer, wherein,

the positive electrode comprises a positive electrode current collector and a positive electrode material loaded on the positive electrode current collector, wherein the surface of the positive electrode material is provided with at least one pit;

the solid electrolyte layer is attached to the entire surface of the pit;

the negative pole includes at least one negative pole district and with the negative pole current collector that the negative pole district electricity is connected, wherein, the negative pole district is formed by the negative pole material who is full of the pit that adheres to solid state electrolyte layer, the negative pole current collector set up in on the surface in negative pole district and with the negative pole district forms the electricity and connects.

2. The solid state battery cell of claim 1, wherein the positive electrode material has a surface with a layer of electrically insulating material disposed thereon to electrically insulate the positive electrode material from the negative electrode current collector.

3. The solid state battery cell with an interdigitated structure of claim 2, wherein the electrically insulating material layer has a through-hole at a location corresponding to the negative electrode region, and the negative electrode current collector has a protrusion matching the through-hole to electrically connect with the negative electrode region through the electrically insulating material layer.

4. The solid state battery cell of claim 1, wherein the dimple is cylindrical, pyramidal, frustoconical, or prismatic in shape.

5. The solid state battery cell with a nested structure of claim 1, wherein the dimples are arranged in an array.

6. The solid state battery cells of claim 5, wherein the array format arrangement is performed by:

the pits are arranged in individual rows along a first direction and are spaced apart within each row in a second direction, wherein the first and second directions are perpendicular to each other and a plane formed by the first and second directions is parallel to an upper surface of the cathode material.

7. The solid-state battery cell with a mutually nested structure of claim 1, wherein the size of the depressions is 100-20000 μm, preferably 100-9000 μm.

8. The solid state battery cell with an interdigitated structure of claim 1, wherein the thickness of the solid state electrolyte layer is 1-100 μ ι η;

preferably, the thickness of the negative electrode current collector is 1 to 50 μm, preferably 1 to 20 μm.

9. The method of preparing a solid-state battery cell with an interdigitated structure according to any one of claims 1 to 8, comprising the steps of:

(1) Loading a positive electrode material on the surface of a positive electrode current collector, and forming at least one pit on the surface of the positive electrode material by pressing;

(2) Attaching a solid electrolyte layer to the entire surface of the pit;

(3) Filling the pit to which the solid electrolyte layer is attached with a negative electrode material to form a negative electrode region;

(4) Electrically connecting a negative current collector to the negative region;

(5) Optionally, before the step (4), forming an electrically insulating material layer on the surface of the cathode material.

10. A series-structured solid-state battery cell constituted by at least two electric core units connected in series through a connection terminal, the electric core units comprising the solid-state battery cell having an interfitting structure as recited in any one of claims 1 to 8.

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