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Silicon Alloying Anodes for High Energy Density Batteries comprising Lithium Rich Cathodes and Safe Ionic Liquid based Electrolytes for Enhanced High VoltagE Performance.

Periodic Reporting for period 1 - Si-DRIVE (Silicon Alloying Anodes for High Energy Density Batteries comprising Lithium Rich Cathodes and Safe Ionic Liquid based Electrolytes for Enhanced High VoltagE Performance.)

Reporting period: 2019-01-01 to 2020-07-31

Widespread market acceptance of electric vehicles (EVs) centres on advances in rechargeable batteries across price, performance, safety, recyclability and suitability for fast charging. Increased adoption of EVs, stimulated by the innovations developed within Si-DRIVE will be an integral part of a greener economy.

Objectives of Si-DRIVE: 1. Development of safe & manufacturable LIB with Si anodes, IL-based solid polymer electrolytes & Li rich cathodes. 2: Achieve beyond SoA full-cell level EDs in two generations. Gen 1: 300-350 Wh/Kg, Gen 2: 350-400 Wh/Kg, providing a pathway to > 450 Wh/kg by 2030. 3: Show capability for fast charging. Gen 1: 2C, 30 mins charge. Gen 2: 6C, 10 mins charge. 4: Demonstrate 500 full-cell cycles (Gen 1) and 1000 cycles (Gen 2) with 80% capacity retention. 5: Show the high sustainability of this new technology and the related cost effectiveness by the application of LCA and LCC approaches and economic viability of recycling with an efficiency >50 weight %. 6: Develop a 2nd life business plan and economic model built upon demonstrator.
Anode Development: Copper silicide nanowire (NW) anodes have been coated with a-Si using ETP by Smit to control a-Si loading and tested in half and full cells (Gen 0 achieved, Gen 1 in process). Anode samples have been sent to partners for full cell tests. Electrochemical studies are underway to find the compatibility of electrolytes received from partners. In parallel, scale up of the anode size (to 5x5 cm2) has been achieved.

Electrolyte Development: Different ionic liquid (IL) families, formed by N-butyl-ammonium and imidazolium cations combined with TFSI or FSI anions, were synthesized. In addition, protic ILs were developed as electrolyte additives to improve the Si anodes compatibility. In total, eleven different ILs were subjected to physicochemical-electrochemical validation and characterization. Several samples of pure ILs and mixed IL electrolytes were provided to Si-DRIVE partners.

Cathode Development: A Co-free LRLO cathode was developed at lab-scale (~5g), which is currently optimized during scale-up (~0.5 kg). The starting stoichiometry was LRLO of Li1.2Ni0.16Mn0.56Co0.08O2 and Co content was reduced to a nominal stoichiometry of Li1.2Ni0.2Mn0.6O2 (LRNM), which showed superior performance than the Co-containing parent compounds. Iron was introduced as a low-cost environmentally benign dopant to stabilize the structure of the LRNM. An initial 400 – 500 g batch of LRNM with electrochemical performance (200~220 mAh g-1 initial reversible capacity) has been distributed to partners.

Full Cell Testing: Full coin cells were assembled with LRLO material (HIU) and a Si-NW anode (UL). The Gen 0 cells at a loading 1mAh/cm2 reached 80% of initial capacity after 214 cycles. Activity was focused on the electrode processing of LRLO Gen 0 material upscaled by ZSW and the full cell harmonisation and electrochemical characterisation of the Gen0 materials at full cell level. The interaction with the different WPs was crucial to obtain the materials and electrodes used to assemble full cells.

Component Modelling: A computational DFT model on benchmark LiMO2 phases (M= Co, Mn, Ni) was performed (CNR). A continuum transport theory was developed (DLR) for pure ionic ILs and mixtures. The full set of equations in Matlab will be a basis for upcoming simulations. Generic results have been obtained that demonstrate the functionality of the model. UL has used Comsol Multiphysics to model the large-deformation expansion of a copper silicide/Si NW of the dimensions relevant to the project. In addition, the possible use of asymptotic homogenization techniques for modelling the anode was also investigated.
Prototype Testing/Validation: During period 1 common testing protocols were defined, to be adopted by all the partners; first cathodic slurry preparation, to verify the rheological parameters in view of the application to comma-roll process. To validate the proposed testing protocols, CID has performed a series of lab scale tests, which have demonstrated that a CCCV step improves the activation of the LRLO from ZSW. The first trial of slurry preparation has shown that the water-based formulations from WP4 are suitable for a comma-roll process.

End of Life, LCC & LCA: The environmental performance of EV battery technologies was examined in preparation for comparison with the first generation of the Si-DRIVE technology. The production process and use of chemicals in recycling are the main drivers for environmental impacts during production and recycling stages. A recycling route was designed that can recycle 50% of the weight of the battery, in accordance with the European Batteries Directive 2006/66/ec. The technical and economic feasibility of using EV batteries in several stationary storage applications are being investigated.

Project Dissemination, Exploitation, Communication & Management: Exploitable results were identified in each work package, and together with the stakeholder strategy, form an integral part of the market watch, IPR and business plan to be developed later in the project . From a management point of view, activities began immediately on the project via a specialist EU project manager. Partners had first contact at the kick off meeting on 21-22 March 2019 (Task 9.1). A quality and risk management plan is integral to optimum management and an initial plan was completed in mM5. This document contains key processes in delivering a high-quality project as well as recognising and mitigating risk.
Anode Development : The electrodes from WP1 are beyond the state of the art (SoA) by addressing the poor electrical conductivity of Si with the copper silicide core and allow the high capacity of a-Si > 3000 mAh/g to be used. The work to-date has shown scaling of the NW electrodes, optimisation of a-Si coating and performance verification. Further scaling of the electrodes, increase of areal loading and incorporation with IL electrolytes in full cells will deliver safer, faster charging and higher energy density (ED) lithium ion batteries.

Electrolyte Development: The IL-electrolytes will be compatible with Si-DRIVE cells operating safely at energy densities (> 400 W h kg-1) and temperatures (i.e. > 100 °C), which are not allowed for commercial Li-ion batteries. The IL components are prepared through an eco-friendly cheaper route, which will allow their full recycling, further contributing to the transitions towards a cleaner energy landscape. The upscaling of the ammonium based ILs, using a continuous synthesis process, is underway.

Cathode Development: The Fe-doped and Co-free LRNM cathode material achieved a specific ED close to 360 Wh kg-1 during initial cycles at 0.1C and maintain more than 200 Wh kg-1 during 200 cycles at 1C. The aqueous processing of the cathode materials, which has been initiated now will improve the environmental impact of the Si-DRIVE cells.

Full Cell Testing : Full coin cells with Si-DRIVE anodes (UL) and cathodes (HIU) retained 80% of initial capacity after 200 cycles.

Component Modelling: Silicon exhibits large volumetric expansion upon charging. In WP5 for the first time the expansion of the cylindrical NWs was simulated.

End of Life, LCC & LCA: The design of Si-drive cells will be progressed toward a novel modular design, design embed disassembly, and computer vision controlled automated disassembly.