Understanding the origins of dendrite formation and growth in LLZO solid electrolytes

Project Information

Den-LLZO

Grant agreement ID: 101110216

DOI

10.3030/101110216

Project closed

EC signature date 18 August 2023

Start date 1 January 2024

End date 31 December 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 214 934,40

Coordinated by

AARHUS UNIVERSITET
Denmark

Periodic Reporting for period 1 - Den-LLZO (Understanding the origins of dendrite formation and growth in LLZO solid electrolytes)

Reporting period: 2024-01-01 to 2025-12-31

Summary of the context and overall objectives of the project

Rechargeable batteries are a key enabling technology for the transition toward sustainable energy systems and the widespread adoption of electric mobility. In particular, solid-state batteries based on lithium metal anodes and ceramic electrolytes such as LLZO offer significant advantages over conventional lithium-ion batteries, including higher energy density and improved safety. However, their practical implementation remains limited by critical reliability challenges, most notably the formation and propagation of lithium dendrites within the solid electrolyte.

Lithium dendrites are filament-like structures that can grow through the electrolyte during battery operation, leading to mechanical degradation, crack formation, and ultimately short-circuiting. Despite extensive research efforts, the fundamental mechanisms governing dendrite initiation and growth in solid electrolytes are not yet fully understood, particularly in the presence of microstructural features such as grain boundaries and defects.

The Den-LLZO project addresses this challenge by aiming to provide a comprehensive and physically grounded understanding of dendrite-induced failure mechanisms in LLZO. The central objective of the project is to identify the critical conditions that lead to dendrite formation and propagation, and to develop predictive modelling tools that can support the design of more reliable solid-state battery materials.

To achieve this, the project adopts a multiscale computational approach that combines atomistic simulations of lithium transport with continuum-level modelling of electro-chemo-mechanical processes. At the atomistic level, lithium diffusion behaviour is investigated in structurally complex environments, while at larger scales, phase-field modelling is used to describe the interaction between lithium accumulation, stress evolution, and crack propagation.

By bridging different length scales and physical processes, the project aims to provide a unified framework for understanding how microscopic transport phenomena translate into macroscopic failure. This integrated approach enables the identification of key factors controlling dendrite-driven degradation and provides insight into how material design and microstructural features influence battery performance.

The expected impact of the Den-LLZO project is to contribute to the development of safer and more reliable solid-state batteries by improving the understanding of their failure mechanisms. In a broader context, this supports ongoing efforts toward sustainable energy technologies, facilitates the adoption of electric vehicles, and contributes to reducing greenhouse gas emissions and dependence on fossil fuels.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the Den-LLZO project, a comprehensive multiscale computational framework was developed to investigate lithium dendrite formation and failure mechanisms in LLZO solid electrolytes. The work combined atomistic simulations and continuum-level modelling to address the complex, coupled processes governing dendrite-driven degradation.

At the atomistic level, molecular dynamics simulations were implemented to study lithium transport in LLZO. A flexible simulation framework was established using LAMMPS, enabling the construction of bulk systems as well as models containing microstructural defects such as grain boundaries and cracks. This framework allowed the systematic investigation of lithium diffusion behaviour in structurally heterogeneous regions. Diffusion coefficients were calculated and lithium migration pathways were identified, providing quantitative insight into transport mechanisms in grain boundaries.

During the execution of this work, a key limitation was identified: the lack of reliable interatomic potentials describing the LLZO–lithium metal interface. This limitation prevented a fully consistent atomistic description of dendrite nucleation and growth. Rather than hindering progress, this finding clarified the modelling boundaries and motivated a refinement of the overall research strategy.

At the continuum level, a phase-field modelling framework was developed to describe dendrite-induced crack growth under coupled electro-chemo-mechanical conditions. The model captures the interaction between lithium concentration, stress evolution, and fracture processes, enabling the simulation of crack initiation and propagation driven by lithium accumulation. This approach provides a predictive description of failure mechanisms in solid electrolytes and represents a major technical achievement of the project.

A central outcome of the project is the integration of atomistic and continuum approaches into a coherent multiscale modelling framework. Atomistic simulations were used to inform transport behaviour, while phase-field modelling captured large-scale fracture processes. This combination enables the translation of microscopic diffusion mechanisms into macroscopic predictions of crack growth and failure.

In addition, the project refined its scientific focus toward crack-driven mechanisms as key pathways for dendrite propagation. This shift, guided by modelling results, provided a more physically consistent understanding of how defects and stress contribute to failure in solid electrolytes.

Overall, the Den-LLZO project successfully achieved its main objectives by (i) establishing atomistic modelling capabilities for lithium transport in LLZO systems with defects, (ii) quantitatively characterizing diffusion behaviour in grain boundaries, (iii) developing a predictive phase-field framework for dendrite-induced crack propagation, and (iv) creating a multiscale modelling approach linking transport and fracture processes. These achievements provide a robust foundation for future research on reliability and failure mechanisms in next-generation solid-state batteries.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The Den-LLZO project advances beyond the current state of the art by providing a physically grounded and predictive description of dendrite-induced failure mechanisms in LLZO solid electrolytes through a multiscale modelling approach. Existing studies often focus either on atomistic lithium transport or on continuum-level mechanical degradation, and typically treat these processes separately. In contrast, this project integrates transport, stress evolution, and fracture within a unified modelling framework.

A key innovation of the project is the development of a phase-field modelling approach that explicitly captures dendrite-induced crack growth under coupled electro-chemo-mechanical conditions. By linking lithium concentration to stress evolution and fracture, the model enables the simulation of crack initiation and propagation driven by lithium accumulation. This represents a significant step beyond simplified or phenomenological approaches, providing a predictive tool for analysing failure in solid electrolytes.

The project also establishes a multiscale modelling strategy that bridges atomistic and continuum descriptions. Atomistic simulations were used to quantify lithium diffusion behaviour and identify migration pathways in grain boundary regions, while continuum phase-field modelling was employed to describe crack propagation at larger scales. This integration enables the translation of microscopic transport behaviour into macroscopic predictions of degradation, which is currently lacking in many existing modelling approaches.

An additional contribution of the project is the identification of key limitations in atomistic modelling of dendrite formation, particularly related to the absence of reliable interatomic potentials for the LLZO–lithium metal interface. Recognizing this limitation allowed the project to adopt a more robust and physically consistent modelling strategy, emphasizing continuum-level descriptions of dendrite-driven fracture processes.

The results provide new insight into the role of microstructural features, such as grain boundaries and crack-like defects, in controlling lithium transport and dendrite propagation. In particular, the identification of critical conditions that trigger crack growth contributes to a more predictive understanding of failure mechanisms in solid electrolytes.

From an application perspective, the developed modelling framework has strong potential to support the design and optimization of solid-state battery materials by enabling the evaluation of reliability and failure risks under different operating and structural conditions. This contributes to addressing key challenges related to battery safety, lifetime, and performance.

Further uptake of the results will require continued development and validation of the models, including improved atomistic descriptions of interfaces and extension to a broader range of materials systems. Future work may also focus on integrating these modelling approaches into materials design workflows and exploring their application in industrial research and development.

Overall, the Den-LLZO project provides a significant advancement in the modelling of dendrite-induced failure by combining multiscale approaches and coupled physical processes, thereby contributing to the development of safer and more reliable next-generation battery technologies.