Heterogeneous solid electrolyte, preparation method and all-solid-state lithium metal battery
Through the design of heterogeneous solid electrolyte, the spontaneous chemical reaction between Li10GeP2S12 with high ionic conductivity and Li7-xPS6-xClx is used to capture lithium dendrites, solving the interface stability of homogeneous electrolytes and significantly improving all-solid lithium metal batteries The current density and cycle stability achieve long-term stable operation and efficient battery performance.
Patent Information
- Application Number
- CN202411069340.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-05
- Publication Date
- 2024-12-20
AI Technical Summary
There are stability problems with homogeneous sulfide solid electrolyte at the interface between the electrode and the solid electrolyte, including space charge layer, interface side reactions and mechanical instability, resulting in a degradation of battery performance.
Using a heterogeneous solid electrolyte, by mixing the first sulfide solid electrolyte Li7-xPS6-xClx with the second sulfide solid electrolyte Li10GeP2S12 with high ionic conductivity, it uses its spontaneous chemical reaction to capture lithium dendrites to generate a beneficial alloy. The phase is increased by increasing the surface migration rate of ions and inhibiting further growth of dendrites.
The critical current density of solid electrolytes and the cycling stability of lithium symmetric batteries have been significantly improved. The modified battery can operate stably for more than 2,000 hours under high current density and maintain an excellent capacity retention rate under normal temperature and high temperature conditions.
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Figure CN119170862A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a non-homogeneous solid electrolyte, a preparation method and an all-solid-state lithium metal battery, belonging to the technical field of all-solid-state lithium batteries. Background Art
[0002] All-solid-state electrolyte lithium metal batteries (ASSBs) have attracted much attention due to their high energy density and safety. Sulfide solid electrolytes (LPSCs), as one of them, have good thermal stability, which helps to improve the safety and cycle stability of the battery. However, sulfide all-solid-state batteries using homogeneous LPSCs have stability issues at the interface between the electrode and the solid electrolyte, including space charge layers, interfacial side reactions, and mechanical instability, which may lead to a decrease in battery performance. Summary of the invention
[0003] In this invention, a heterogeneous solid electrolyte is constructed, and the attraction of the electrolyte with high ionic conductivity in the heterogeneous solid electrolyte to the growth of dendrites is utilized, and the spontaneous chemical reaction between the electrolyte and metallic lithium is utilized to capture lithium dendrites and generate a beneficial alloy phase, thereby increasing the surface migration rate of ions and inhibiting the further growth of dendrites.
[0004] The technical solution of the present invention is:
[0005] A heterogeneous solid electrolyte comprises a first sulfide solid electrolyte and a second sulfide solid electrolyte, wherein the ion conductivity of the second sulfide solid electrolyte is greater than that of the first sulfide solid electrolyte, and the second sulfide solid electrolyte can react with lithium.
[0006] The heterogeneous solid electrolyte is applied to all-solid-state lithium metal batteries.
[0007] The first sulfide solid electrolyte is LPSC; and the LPSC preferably has the chemical formula Li 7-x PS 6-x Cl x , 0≤x≤1.0.
[0008] The second sulfide solid electrolyte can spontaneously undergo a chemical reaction with lithium, and the chemical reaction will not be rapidly passivated due to interface products.
[0009] The second sulfide solid electrolyte is Li 10 GeP2S 12 (LGPS).
[0010] The weight ratio between the first sulfide solid electrolyte and the second sulfide solid electrolyte is 7:3-9:1.
[0011] The method for preparing the above-mentioned heterogeneous solid electrolyte comprises the following steps:
[0012] The first sulfide solid electrolyte and the second sulfide solid electrolyte are mixed and then ball-milled.
[0013] The ball milling speed is 50-100 rpm, and the ball milling time is 5-15 h.
[0014] An all-solid-state lithium metal battery comprises the above-mentioned heterogeneous solid electrolyte.
[0015] A performance evaluation test method for an all-solid-state lithium metal battery comprises the following steps:
[0016] Assembling a battery using the above-mentioned heterogeneous solid electrolyte and performing charging and discharging;
[0017] Detection of reduced Ge at the anode / electrolyte interface 0 ;
[0018] And make the following judgment: 0 The resulting battery has better cycle performance.
[0019] Beneficial Effects
[0020] The non-solid electrolyte of the present invention significantly improves the critical current density of the solid electrolyte from 0.5 mA / cm 2 , increased to 2.1mA / cm 2 The cycling stability of the lithium symmetric battery has also been significantly improved. The unmodified LPSC1.0 electrolyte can only last for less than 20 hours (0.3mA / cm 2 ,0.3mAh / cm 2 ), the modified heterogeneous electrolyte can operate stably for 17,000 hours and can also operate at high current density (1.0 mA / cm 2 ,1.0mAh / cm 2 ) can operate stably for more than 2000 hours. 0.8 Co 0.1 Mn 0.1 The O2 (denoted as NCM811) full battery also showed excellent performance. At 60 degrees, the capacity retention rate of 500 cycles was 80.4% (1.0 mA / cm 2 ). Under normal temperature conditions, the capacity retention rate after 200 cycles is 84.3% (1.0 mA / cm 2 ). BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1. Schematic diagram of the design mechanism of heterogeneous electrolytes. a, Schematic diagram of the construction of homogeneous electrolytes. Homogeneous solid electrolytes create uniform ion transmission flux; b, Schematic diagram of the construction of heterogeneous electrolytes. Heterogeneous solid electrolytes create non-uniform ion transmission flux; c, Homogeneous electrolytes can be simplified into a parallel circuit composed of a group of equal resistors. The same resistance value leads to the same current passing through each resistor; d, Heterogeneous electrolytes can be simplified into a parallel circuit composed of a group of non-equivalent resistors. The smaller the resistance value, the greater the current passing through the resistor;
[0022] Figure 2 . Critical current density test based on different solid electrolytes. a, LPSC1.0 electrolyte; b, LPSC1.0-91 electrolyte; c, LPSC1.0-82 electrolyte; d, LPSC1.0-73 electrolyte
[0023] Figure 3 .Cold pressure ionic conductivity test of several electrolytes;
[0024] Figure 4 .Voltage-areal capacity curves of lithium symmetric batteries based on LPSC1.0-82 and LPSC1.0-73 heterogeneous electrolytes
[0025] Figure 5 .a, Cycling performance of lithium symmetric battery based on LPSC1.0 electrolyte (0.3 mA / cm 2 ,0.3mAh / cm 2 ); b, Cyclic performance of lithium symmetric battery based on LPSC1.0-82 heterogeneous electrolyte (0.3 mA / cm 2 ,0.3mAh / cm 2 );
[0026] Figure 6 Cycling performance of lithium symmetric batteries based on LPSC1.0-82 heterogeneous electrolyte under high current conditions (1.0 mA / cm 2 ,1.0mAh / cm 2 );
[0027] Figure 7 .a, Critical current density test of LPSC1.25 electrolyte; b, Critical current density test of LPSC1.5 electrolyte; c, Critical current density test of LPSC1.25-82 electrolyte; d, Critical current density test of LPSC1.5-82 electrolyte; e, Li symmetric battery based on LPSC1.0-82 electrolyte after 10 cycles (0.5mA / cm 2 ,0.5mAh / cm 2) of the lithium / electrolyte interface products; f, lithium symmetric battery based on LPSC1.25-82 electrolyte after 10 cycles (0.5 mA / cm 2 ,0.5mAh / cm 2 ) of the lithium / electrolyte interface products; g, lithium symmetric battery based on LPSC1.5-82 electrolyte after 10 cycles (0.5 mA / cm 2 ,0.5mAh / cm 2 )’s XPS analysis of lithium / electrolyte interface products;
[0028] Figure 8 .a, X-ray diffraction curves of several electrolytes; b, ionic conductivity tests of several electrolytes;
[0029] Fig. 9 Electrochemical performance of Li||NCM811 all-solid-state batteries based on LPSC1.0-82 or LPSC1.0 electrolyte at room temperature: a, rate performance; b, charge and discharge curves at different current densities; c, charge and discharge curves based on LPSC1.0 electrolyte; d, cycle performance curve;
[0030] Fig.10 Electrochemical performance of Li||NCM811 all-solid-state batteries based on LPSC1.0-82 or LPSC1.0 electrolyte at 60°C: a, rate performance; b, charge and discharge curves at different current densities; c, charge and discharge curves based on LPSC1.0 electrolyte; d, cycle performance curve;
[0031] Fig.11 In-situ impedance test of symmetric batteries based on LPSC1.0-82 or LPSC1.0-73 electrolytes during cycling. a, LPSC1.0-82 electrolyte; b, LPSC1.0-73 electrolyte. DETAILED DESCRIPTION
[0032] Figure 1 This is the technical concept of the heterogeneous electrolyte in this patent: for traditional homogeneous electrolytes, since the electrolyte particles are uniform, the potential barriers of the migration paths through which ions pass are the same, resulting in a uniform ion transmission flux. The model can be simplified into a set of parallel circuits composed of equal resistors, each resistor represents a different path for ion transmission, and the current passing through the resistor is the flux of ion transmission. According to Ohm's law, the same resistance means the same current. For heterogeneous electrolytes, due to the differences in the electrolyte particles, the potential barriers of the ion transmission paths will be different, that is, the ion transmission flux is uneven. Heterogeneous electrolytes can be simplified into a set of parallel circuits composed of non-equivalent resistors, and for these low migration barrier paths, they have a higher ion transmission flux.
[0033] Example 1
[0034] LPSC1.0 is combined with Li 10 GeP2S 12 (denoted as LGPS) A series of heterogeneous electrolytes were constructed by mixing at different ratios through low-speed ball milling (50-100rpm), namely LPSC1.0:LGPS=9:1 (mass ratio, denoted as LPSC1.0-91); LPSC1.0:LGPS=8:2 (mass ratio, denoted as LPSC1.0-82); LPSC1.0:LGPS=7:3 (mass ratio, denoted as LPSC1.0-73). Low-speed ball milling does not affect the ionic conductivity of the electrolyte ( Figure 3 ).
[0035] Comparative Example
[0036] The electrolyte LPSC1.0 before modification was used as a control.
[0037] Comparison of critical current density:
[0038] The critical current density of several heterogeneous electrolytes in Example 1 is as follows: Figure 2 As shown in bd, they are 0.7, 2.1, and 2.9 mA / cm 2 However, adding too much LGPS will lead to a decrease in the stability of the heterogeneous electrolyte to the lithium interface, such as Figure 4 shown, and in Fig.11 It can be seen that the impedance of the symmetric battery with LPSC 1.0-73 electrolyte gradually increases during the cycle, while that of LPSC 1.0-82 remains basically unchanged. In the critical current density test, the critical current density of the lithium symmetric battery assembled based on the unmodified electrolyte LPSC1.0 was only 0.5 mA / cm 2 ( Figure 2 a).
[0039] Assembly of lithium symmetric battery:
[0040] First, add about 150mg of solid electrolyte powder into a solid-state battery mold with a dendrite of 10mm, apply 2 tons of pressure, maintain pressure for 2 minutes, and place 9mm diameter 100 micron thick lithium sheets on both sides of the solid electrolyte. Finally, apply external stacking pressure to the solid-state battery mold through an external fixture. The pressure is controlled by a torque wrench with a torque of 2-4Nm.
[0041] The cycling stability of the lithium symmetric battery has also been significantly improved. The original LPSC1.0 electrolyte has a cycling stability of 0.3 mA / cm 2At a current density of 1.0 mA / cm2, it can only last for less than 20 hours, while the heterogeneous electrolyte LPSC1.0-82 can stably operate for more than 17,000 hours. 2 ), the heterogeneous electrolyte LPSC1.0-82 can also operate stably for more than 2000 hours.
[0042] In order to explore the intrinsic mechanism of the heterogeneous electrolyte in inhibiting dendrite growth, two argyrodite electrolytes with higher chlorine content were prepared. X-ray diffraction showed that they were pure phase ( Figure 8 a), respectively Li 5.75 PS 4.75 Cl 1.25 (denoted as LPSC1.25) and Li 5.5 PS 4.5 Cl 1.5 (denoted as LPSC1.5). The ionic conductivity of the electrolyte increases with the increase of chlorine content ( Figure 8 b). The critical current density of the two electrolytes is 0.7 mA / cm 2 and 0.9mA / cm 2 , slightly higher than 0.5mA / cm of LPSC1.0 2 The heterogeneous electrolytes LPSC1.25-82 and LPSC1.5-82 based on LPSC1.25 or LPSC1.5 were then prepared in the same way, with a critical current density of 1.5 mA / cm 2 and 1.1mA / cm 2 . It can be seen that with the increase of chlorine content, the effect of heterogeneous electrolyte in inhibiting dendrites gradually becomes worse, which is related to the ionic conductivity of the solid electrolyte that constitutes the heterogeneous electrolyte. For LPSC1.0-82, the ionic conductivity of LPSC1.0 is lower than that of LGPS. Therefore, LGPS, as a high ionic conductivity phase of the heterogeneous electrolyte, has a higher ion transfer flux through it, so LGPS also has a stronger attraction to dendrites. As the chlorine content increases, the ionic conductivity of LGPS gradually loses its advantage, and the attraction to dendrites gradually weakens. Therefore, the effect of heterogeneous electrolyte in inhibiting dendrites gradually becomes worse.
[0043] By detecting the reduced Ge at the anode / electrolyte interface 0 ( Figure 7 The results show that the Ge of LPSC1.0-82 has a great influence on the reaction between the negative electrode and the LGPS electrolyte, and the attraction effect of LGPS on the corresponding dendrites in different heterogeneous electrolytes can be compared. 0The intensity of is the highest, indicating that the amount of metallic lithium reacting with it is the most, proving that the LGPS has the strongest attraction effect on the growth of dendrites.
[0044] In the above reaction process, the reaction principle is:
[0045] Li+Li 10 GeP2S 12 =Li3Ge+Li3P+Li2S+LiCl, where Li3Ge is an electronic conductor, and the latter three are ionic conductors. The interface products are mixed conductors, so the interface cannot be passivated. The interface reaction between LPSC and metallic lithium will be passivated by byproducts, and dendrites will not be consumed, so they can grow rapidly. LGPS can react all the growing dendrites, so the dendrite problem has little effect on LGPS.
[0046] Assembly preparation of the full cell:
[0047] Add about 150mg of solid electrolyte powder to the solid-state battery mold, first press the electrolyte powder into shape with a pressure of 1 ton, then evenly add a certain amount (about 5mg) of composite positive electrode powder on the positive electrode side of the solid electrolyte, and then cold press it with a pressure of 2 tons. Then put a 9mm diameter 100 micron thick lithium sheet on the negative electrode side of the solid electrolyte, and finally apply external stacking pressure to the solid-state battery mold through an external fixture. The pressure is controlled by a torque wrench, and the torque is 5-7Nm.
[0048] The performance of the full battery based on heterogeneous electrolyte has also been significantly improved. For the original LPSC1.0 electrolyte, the all-solid-state battery can only last for one cycle at room temperature and short-circuit in the second cycle ( Fig. 9 c). Under high temperature conditions, short circuit occurs only in the third turn ( Fig.10 c). The all-solid-state battery based on LPSC1.0-82 heterogeneous electrolyte exhibits excellent rate performance and cycle stability. Under normal temperature conditions, it can stably cycle 200 times with a retention rate of 84.3%. At 60 degrees, it can stably operate for 500 cycles with a retention rate of over 80%.
Claims
1. A heterogeneous solid electrolyte, characterized in that: The invention comprises a first sulfide solid electrolyte and a second sulfide solid electrolyte, wherein the ion conductivity of the second sulfide solid electrolyte is greater than the ion conductivity of the first sulfide solid electrolyte, and the second sulfide solid electrolyte can react with lithium.
2. The heterogeneous solid electrolyte according to claim 1, characterized in that: The heterogeneous solid electrolyte is applied to all-solid-state lithium metal batteries.
3. The heterogeneous solid electrolyte according to claim 1, characterized in that: The first sulfide solid electrolyte is LPSC; and the LPSC preferably has the chemical formula Li 7-x PS 6-x Cl x , 0≤x≤1.
0.
4. The heterogeneous solid electrolyte according to claim 1, characterized in that: The second sulfide solid electrolyte can spontaneously react chemically with lithium.
5. The heterogeneous solid electrolyte according to claim 1, characterized in that: The second sulfide solid electrolyte is Li 10 GeP2S 12 (LGPS).
6. The heterogeneous solid electrolyte according to claim 1, characterized in that: The weight ratio between the first sulfide solid electrolyte and the second sulfide solid electrolyte is 7:3-9:
1.
7. The method for preparing the heterogeneous solid electrolyte according to claim 1, characterized in that: The method comprises the following steps: mixing a first sulfide solid electrolyte and a second sulfide solid electrolyte and then ball milling the mixture; the ball milling speed is 50-100 rpm.
8. An all-solid-state lithium metal battery, characterized in that: The method comprises the heterogeneous solid electrolyte according to any one of claims 1 to 6.
9. A performance evaluation test method for an all-solid-state lithium metal battery, characterized in that: The steps include: Assembling a battery using the heterogeneous solid electrolyte according to claim 1, and performing charging and discharging; Detection of reduced Ge at the anode / electrolyte interface 0 ; And make the following judgment: 0 The resulting battery has better cycle performance.
10. Use of the heterogeneous solid electrolyte according to any one of claims 1 to 6 in an all-solid-state lithium metal battery.