As per Grant agreement the consortium has set up four operational objectives:
1. Designing and prototyping the high energy density gellified cell concept
By the first trimester of the project the technical specification and KPI´s are defined by WP2 then the electrical, Safety and lifetime requirements based on the user cases are determined by M16 with WP2. The details could be found in the work package 2 section. Besides to evaluate the battery cell performances a test protocol has been developed during the first year of the project
2. Developing gellified cell materials and components
Separators and electrolyte:
NEXTCELL is pending the identification of a suitable electrolyte for the Si-C / LNMO system. Gen1d or Gen0 seem to be the best candidates as trapped electrolyte for the electrodes for the moment. But permanent trapping has to be improved.
Cathodes:
LMNO gen1 exhibits promising performances in cycling with LPx electrolyte (1M LiPF6 in EC:DMC:EMC 1:1:1), but this electrolyte does not suit with solventless process (too low boiling point). LMNO gen 1 exhibits good performances in cycling with the Gen0 electrolyte, but they remain quite poorer, compared to LPx. They seem better with the Gen1d electrolyte, but less relevant than with LPx.
The LMNO gen1 implementation in gelled electrode through solventless process is feasible with the Gen0 electrolyte. However, the best formulations as the optimized process parameters are not still determined, the objective being to reach the same performances in cycling as those achieved in classical electrode with the same electrolyte
The LMNO gen 1 implementation in gelled electrode through solventless process is feasible with the Gen1d electrolyte. However, the electrolyte trapping seems not to be permanent:
Anodes:
Si-C, gen1 exhibits a specific capacity of 775 mAh/g with 1M LiPF6 in EC: DEC 1:1 +2%VC +10% FEC. Unfortunately, this electrolyte does not suit with the solventless process (too low boiling points). It exhibits quite similar performances with the Gen0 + FEC electrolyte.
To achieve the highest electrode energy density as possible, the Si-C, gen1 was implemented in gelled electrode with the Gen0 electrolyte or Gen1d electrolyte with a ratio of 95% (related to the solid part). The electrode can be prepared, provided that the electrolyte content is of 30% at least, that is not favorable to a high energy density. Below, the electrode is fragile and therefore difficult to be laminated. In addition, the electrolyte trapping, especially with Gen1d, seems not to be permanent.
Si-C, gen2 with higher specific capacity close to 1000 mAh/g is announced by NMKS. Its particle size will be investigated to facilitate the extrusion step, and consequently the lamination and co-lamination ones.
Conductive carbons:
Nextcell project successfully developed and selected a grade of CNT that will improve performance with as low as 0.5% content, proven with 4-point film resistivity test, as reported in D3.2.
Finally, further validation and application will be done in the next stages.
3. Deepening the knowledge: modelling the gellified cell concept.
WP7 aims to develop digital tools to study the phenomena of interest in the NEXTCELL gel system for the three strategic aspects of battery development, which are improving performance, understanding and controlling the aging of materials and the eventual elimination of safety problems. Three approaches were implemented during the first phase of the project work: 1) A first task consists of setting up tools characterizing the performances of the cells by simulating the architecture of the electrodes and by optimizing the microstructures. Virtual microstructures are generated via the software LIGGGHTS and incorporating in a Multiphysics software COMSOL Multiphysics for resolved electrochemical solicitation. 2) A second task is to simulate the charge of a SiC particle, including the thermomechanical dynamics relating to the diffusion of lithium. The approach involved modelling the distribution of a multi-domain particle and a new formulation of the governing partial differential equation to capture the mechanical aspect. For this purpose, a new code based on the finite element method has been developed. In parallel, a SEI growth model was developed to describe the chemical nature of this passivation layer which is responsible for a large part of the aging of electrode materials. Finally, 3) a mathematical approach to the kinetics resolution of thermal runaway for safety model is implemented.
4. Ensuring the replication and dissemination of NEXTCELL’s results
WP9 has made strong progress in raising project awareness, thanks to the communication and dissemination efforts spearheaded by SIE in collaboration with the entire consortium. This includes attending numerous events, initiating clustering activities with related initiatives, and submitting abstracts to align with open science principles. Additionally, the project’s original key exploitable results have been refined and are under ongoing review to ensure successful future exploitation.
