A method of inhibiting grain growth along grain boundaries in LLZO solid state electrolytes and simulation method

Abstract

The application discloses a method for inhibiting the growth of dendrites along the grain boundary in an LLZO solid-state electrolyte and a simulation method, and the method comprises adding a metal element with a Young's modulus smaller than that of the LLZO solid-state electrolyte to the LLZO solid-state electrolyte.The method for inhibiting the growth of dendrites in the application utilizes the difference in the Young's modulus of electrolyte materials to affect the growth of dendrites along the grain boundary.The doped part of the material with a lower Young's modulus can inhibit the growth of dendrites therein, and the material with a higher Young's modulus is contrary.The part with a lower Young's modulus is more prone to deformation when facing the extrusion of growing dendrites, so as to slow down the penetration of the dendrites.

Description

Technical Field

[0001] This invention relates to a method and simulation method for suppressing dendrite growth along grain boundaries in LLZO solid electrolyte. Background Technology

[0002] Lithium-ion batteries are widely used in new energy vehicles and other fields, but traditional lithium-ion batteries are gradually reaching their theoretical energy density limit, and liquid flammable electrolytes also face safety challenges. Solid-state electrolytes have higher theoretical energy density than traditional electrolytes and are also more advantageous in terms of safety.

[0003] However, solid-state electrolytes, like liquid electrolytes, still face the problem of short-circuit failure due to dendrite growth. During charging and discharging, lithium ions can precipitate unevenly, easily forming dendrites. These dendrites grow continuously with each cycle, eventually breaking down the electrolyte, causing a short circuit and leading to serious battery failure and safety issues. Theoretically, solid-state electrolytes, due to their rigidity, should not be broken down by lithium dendrites. However, in reality, lithium dendrites can still penetrate solid-state electrolytes in experiments. Defects in the electrolyte material have a significant impact on dendrite growth; grain boundaries are also a type of defect. This patent aims to provide a method to extend battery cycle life and reduce the impact of dendrite penetration by inhibiting the growth of lithium dendrites along the grain boundaries of LLZO solid-state electrolytes. Summary of the Invention

[0004] The present invention provides a method and simulation method for suppressing dendrite growth along grain boundaries in LLZO solid electrolyte in order to solve the problems existing in the prior art.

[0005] The technical solutions adopted in this invention are as follows: A method for suppressing dendrite growth along grain boundaries in LLZO solid electrolyte involves adding a metal element to the LLZO solid electrolyte with a Young's modulus lower than that of the LLZO solid electrolyte itself.

[0006] Furthermore, the metallic element is Al, Ge, Ga, or Sc.

[0007] This invention also discloses a method for suppressing dendrite growth along grain boundaries in LLZO solid electrolyte based on COMSOL software simulation. Four simulation models are established in COMSOL software, corresponding to: LLZO solid electrolyte model, X-LLZO solid electrolyte model with metal element X, composite model A and composite model B with LLZO solid electrolyte and X-LLZO solid electrolyte. When the composite model A and composite model B are established, the Young's modulus of the models is set so that both composite model A and composite model B are divided into upper and lower layers. The lower layer of composite model A is a non-uniform X-LLZO solid electrolyte, and the upper layer is a uniform LLZO solid electrolyte; the upper layer of composite model B is a non-uniform X-LLZO solid electrolyte, and the lower layer is a uniform LLZO solid electrolyte. Four models of dendrite growth were simulated, and the growth was plotted over time. The plot showed that if the Young's modulus of the doped metal element is less than that of the LLZO solid electrolyte itself, dendrite growth can be suppressed, and vice versa.

[0008] Furthermore, composite model A and composite model B are divided into two equal parts by setting the Young's modulus of the models.

[0009] Furthermore, the logic for dividing composite model A and composite model B based on their Young's modulus is as follows: if the Young's modulus of the models are the same, it indicates that no metal element is doped; if they are different, it indicates that metal element is doped.

[0010] The present invention has the following beneficial effects: The method for suppressing dendrite growth in this invention utilizes the difference in Young's modulus of the electrolyte materials to influence dendrite growth along grain boundaries. Doped portions of the material with lower Young's modulus suppress dendrite growth within them, while those with higher Young's modulus have the opposite effect. The portions with lower Young's modulus are more prone to deformation when subjected to the pressure of growing dendrites, thus slowing down dendrite penetration. Attached Figure Description

[0011] Figure 1 The diagrams show the model of an LLZO electrolyte with uniform grain boundaries and the model of an Al-LLZO electrolyte with non-uniform grain boundaries doped with aluminum.

[0012] Figure 2 The diagram shows two composite solid electrolyte models based on LLZO and Al-LLZO solid electrolytes.

[0013] Figure 3 The diagram shows the dendrite growth in the four models after 600 seconds of simulation.

[0014] Figure 4 The diagram shows the dendrite growth in the four models after 900 seconds of simulation.

[0015] Figure 5 A graph created based on the simulation results. Detailed Implementation

[0016] The following is in conjunction with the appendix Figure 1-5 The present invention will be further described below.

[0017] This embodiment uses A1 as an example to describe the invention in detail.

[0018] COMSOL was used to simulate the growth of dendrites in LLZO solid electrolytes with different grain boundary structures.

[0019] The phase-field model was refined for specific LLZO materials: LLZO solid electrolytes with uniform particle size and Al-LLZO solid electrolytes doped with aluminum. The models showed no internal defects (pores, surface cracks, etc.) except at grain boundaries, meaning that dendrite deposition always started from one side of the electrode and spread to the other. The phase transition process began at the dendrite tip and gradually evolved along the grain boundaries. This evolution process was characterized by phase-field simulation.

[0020] Model design such as Figure 1 The lower side has a lithium metal electrode in contact with the solid electrolyte. In both models, the upper displacement is set to be fixed by Dirichlet boundary conditions. Based on two known solid-state battery models, two composite models are designed: composite model A and composite model B, which have LLZO solid electrolyte and X-LLZO solid electrolyte respectively.

[0021] Both composite model A and composite model B are divided into upper and lower layers, with different electrolytes used in each layer, so that dendrites grow along the grain boundary gaps of different structures.

[0022] Composite model A consists of a non-uniform Al-LLZO solid electrolyte in the lower layer and a uniform LLZO solid electrolyte in the upper layer. Composite model B consists of a non-uniform Al-LLZO solid electrolyte on top and a uniform LLZO solid electrolyte on the bottom. The rest of the design remains the same as the original. The models for the two novel designs are as follows: Figure 2 The logic for dividing composite model A and composite model B based on their Young's modulus is as follows: if the Young's modulus of the models are the same, it indicates that no metal element is doped; if they are different, it indicates that metal element is doped.

[0023] Four models of dendrite growth were simulated, and the growth data were organized according to time as follows: Figure 5 One of the composite models exhibits superior performance. In the initial stage of dendrite growth, the electrochemical driving force has a significant impact on dendrite growth, while the LLZO material with its large Young's modulus has little effect on promoting it. However, when the dendrites reach the grain boundaries of the Al-LLZO material, the Al doping portion with its smaller Young's modulus inhibits their growth, thus slowing down the dendrite growth rate and improving cycle life.

[0024] Further analysis of the simulation results reveals that electrolytes with higher Young's modulus promote dendrite growth, while electrolytes with lower Young's modulus relatively inhibit it. The portion with a higher Young's modulus is less prone to deformation when subjected to dendrite growth-induced compression, allowing the dendrites to continue growing along the grain boundaries; conversely, the portion with a lower Young's modulus is more prone to deformation, thus inhibiting dendrite growth to some extent. Compared to LLZO electrolytes, the Al-doped portion of Al-LLZO has a lower Young's modulus. Therefore, when dendrites grow into the Al-doped portion, their growth is suppressed compared to when they grow in the LLZO portion. In composite model B, the dendrites in the latter half of the simulation grow in the Al-LLZO portion, and their growth rate is suppressed compared to the dendrite growth in LLZO in composite model A during the same time period. In this invention, "larger" (or "higher") refers to a Young's modulus greater than that of the LLZO solid electrolyte itself, and "smaller" (or "lower") refers to a Young's modulus less than that of the LLZO solid electrolyte itself.

[0025] The method for suppressing dendrite growth in this invention utilizes the difference in Young's modulus of the electrolyte materials to influence dendrite growth along grain boundaries. Doped portions of the material with lower Young's modulus suppress dendrite growth within them, while those with higher Young's modulus have the opposite effect. The portions with lower Young's modulus are more prone to deformation when subjected to the pressure of growing dendrites, thus slowing down dendrite penetration.

[0026] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for suppressing dendrite growth along grain boundaries in LLZO solid electrolyte based on COMSOL software simulation, characterized in that: Four simulation models were established in COMSOL software, corresponding to: LLZO solid electrolyte model, X-LLZO solid electrolyte model with metal element X, composite model A and composite model B with LLZO solid electrolyte and X-LLZO solid electrolyte. When the composite model A and composite model B are established, the Young's modulus of the models is set so that both composite model A and composite model B are divided into upper and lower layers. The lower layer of composite model A is a non-uniform X-LLZO solid electrolyte, and the upper layer is a uniform LLZO solid electrolyte; the upper layer of composite model B is a non-uniform X-LLZO solid electrolyte, and the lower layer is a uniform LLZO solid electrolyte. Four dendrite growth models were simulated, and the growth was plotted over time. In the simulation, the dendrites in composite model B grew in the Al-LLZO region in the latter half of the process. Compared with the dendrites in composite model A growing in LLZO in the same time period, the growth rate of the dendrites was suppressed. The metallic element is Al.

2. The method for suppressing dendrite growth along grain boundaries in LLZO solid electrolyte based on COMSOL software simulation as described in claim 1, characterized in that: Composite model A and composite model B are divided into two equal parts by setting the Young's modulus of the models.

3. The method for suppressing dendrite growth along grain boundaries in LLZO solid electrolyte based on COMSOL software simulation as described in claim 2, characterized in that: The logic for dividing composite model A and composite model B based on their Young's modulus is as follows: if the Young's modulus of the models are the same, it means that no metal element is doped; if they are different, it means that metal element is doped.

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