Quentin Jacquet

CEA Grenoble

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Co-Authors

Gwenaëlle Rousse

Collège de France

Jean‐Marie Tarascon

Collège de France

Clare P. Grey

University of Cambridge

Sandrine Lyonnard

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Antonella Iadecola

Réseau sur le Stockage Electrochimique de l'énergie

Clémence Alasseur

Électricité de France (France)

Alice J. Merryweather

University of Cambridge

Artem M. Abakumov

Skolkovo Institute of Science and Technology

Christoph Schnedermann

University of Cambridge

Wim van Ackooij

Électricité de France (France)

Cooperative Institutions

Centre National de la Recherche Scientifique

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Université Grenoble Alpes

Réseau sur le Stockage Electrochimique de l'énergie

CEA Grenoble

European Synchrotron Radiation Facility

Collège de France

Chimie du Solide et Energie

University of Cambridge

CEA LITEN

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Charge Transfer Band Gap as an Indicator of Hysteresis in Li-Disordered Rock Salt Cathodes for Li-Ion Batteries

Journal of the American Chemical Society (2019)

Quentin Jacquet Antonella Iadecola Matthieu Saubanère Haifeng Li Erik J. Berg

Disordered rock salt cathodes showing both anionic and cationic redox are being extensively studied for their very high energy storage capacity. Mn-based disordered rock salt compounds show much higher energy efficiency compared to the Ni-based materials as a result of the different voltage hysteresis, 0.5 and 2 V, respectively. To understand the origin of this difference, we herein report the design of two model compounds, Li1.3Ni0.27Ta0.43O2 and Li1.3Mn0.4Ta0.3O2, and study their charge compensation mechanism through the uptake and removal of Li via an arsenal of analytical techniques. We show that the different voltage hysteresis with Ni or Mn substitution is due to the different reduction potential for anionic redox. We rationalized such a finding by DFT calculations and propose this phenomenon to be nested in the smaller charge transfer band gap of the Ni-based compounds compared to that of the Mn ones. Altogether, these findings provide vital guidelines for designing high-capacity disordered rock salt cathode materials based on anionic redox activity for the next generation of Li ion batteries.

Hysteresis

Cationic polymerization

10.1021/jacs.8b11413

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A Quadratic Regularization for the Multi-Attribute Unit-Demand Envy-Free Pricing Problem

arXiv (Cornell University) (2021)

Quentin Jacquet Wim van Ackooij Clémence Alasseur Stéphane Gaubert

We consider a profit-maximizing model for pricing contracts as an extension of the unit-demand envy-free pricing problem: customers aim to choose a contract maximizing their utility based on a reservation price and multiple price coefficients (attributes). Classical approaches suppose that the customers have deterministic utilities; then, the response of each customer is highly sensitive to price since it concentrates on the best offer. To circumvent the intrinsic instability of deterministic models, we introduce a quadratically regularized model of customer's response, which leads to a quadratic program under complementarity constraints (QPCC). This provides an alternative to the classical logit approach, still allowing to robustify the model, while keeping a strong geometrical structure. In particular, we show that the customer's response is governed by a polyhedral complex, in which every polyhedral cell determines a set of contracts which is effectively chosen. Moreover, the deterministic model is recovered as a limit case of the regularized one. We exploit these geometrical properties to develop a pivoting heuristic, which we compare with implicit or non-linear methods from bilevel programming, showing the effectiveness of the approach. Throughout the paper, the electricity provider problem is our guideline, and we present a numerical study on this application case.

Regularization

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Magnetic and Intercalation Properties of BaRu₂O₆ and SrRu₂O₆

Chemistry of Materials (2020)

Thomas Marchandier Gwenaëlle Rousse Quentin Jacquet Artem M. Abakumov François Fauth

Ruthenium oxides have been extensively studied for their attractive magnetic properties. For instance, the honeycomb-layered ruthenate SrRu2O6 has attracted a lot of attention in the last years for its unusually high Néel temperature (565 K), which is among the highest for 4d transition-metal oxides. Motivated by this intriguing feature, several authors suggested to tune the magnetic properties via atomic substitutions. However, in spite of intense efforts, this could not happen because of the instability of the targeted phases at high temperature. We unlocked this bottleneck and succeeded in synthetizing the Ba-based analogue BaRu2O6 by a microwave-assisted hydrothermal process. We describe herein for the first time its structure and physico-chemical properties. Synchrotron X-ray, neutron powder diffraction, and transmission electron microscopy confirm this new compound to be structurally related to SrRu2O6 with however a different oxygen layer stacking. Thereafter, BaRu2O6 is shown to be an antiferromagnet with a high Néel temperature (525 K), and this behavior is discussed in light of its crystal structure. Finally, both SrRu2O6 and BaRu2O6 can electrochemically insert lithium, and the interlayer alkali-earth cations act as pillars, which strongly affect the structural evolution through lithiation. Our results offer new keys toward a better understanding of the magnetic and electrochemical properties of complex ruthenium-based layered oxides.

10.1021/acs.chemmater.0c02469

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Ergodic control of a heterogeneous population and application to electricity pricing

IEEE Transactions on Automatic Control (2025)

Quentin Jacquet Wim van Ackooij Clémence Alasseur Stéphane Gaubert

Electricity pricing

10.1109/tac.2025.3532178

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Ergodic control of a heterogeneous population and application to electricity pricing

arXiv (Cornell University) (2022)

Quentin Jacquet Wim van Ackooij Clémence Alasseur Stéphane Gaubert

We consider a control problem for a heterogeneous population composed of agents able to switch at any time between different options. The controller aims to maximize an average gain per time unit, supposing that the population is of infinite size. This leads to an ergodic control problem for a "mean-field" Markov Decision Process in which the state space is a product of simplices, and the population evolves according to controlled linear dynamics. By exploiting contraction properties of the dynamics in Hilbert's projective metric, we prove that the infinite-dimensional ergodic eigenproblem admits a solution and show that the latter is in general non unique. This allows us to obtain optimal strategies, and to quantify the gap between steady-state strategies and optimal ones. In particular, we prove in the one-dimensional case that there exist cyclic policies -- alternating between discount and profit taking stages -- which secure a greater gain than constant-price policies. On numerical aspects, we develop a policy iteration algorithm with "on-the-fly" generated transitions, specifically adapted to decomposable models, leading to substantial memory savings. We finally apply our results on realistic instances coming from an electricity pricing problem encountered in the retail markets, and numerically observe the emergence of cyclic promotions for sufficient inertia in the customer behavior.

10.48550/arxiv.2204.01410

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Operando monitoring of single-particle kinetic state-of-charge heterogeneities and cracking in high-rate Li-ion anodes

arXiv (Cornell University) (2021)

Alice J. Merryweather Quentin Jacquet Steffen Emge Christoph Schnedermann Akshay Rao

Recent years have seen a rapidly escalating demand for battery technologies capable of storing more energy, charging more quickly and having longer usable lifetimes, driven largely by increased electrification of transport and by grid-scale energy storage systems. This has led to the development of many promising new electrode materials for high-rate lithium ion batteries. In order to rationalise and improve upon material performance, it is crucial to understand the fundamental ion-intercalation and degradation mechanisms occurring during realistic battery operation, on the nano- to meso-scale. Here we apply a straightforward laboratory-based operando optical scattering microscopy method to study micron-sized rods of the high-rate anode material Nb$_{14}$W$_3$O$_{44}$ during cycling at rates of up to 30C. We directly visualise an elongation of the rods, which, by comparison with ensemble X-ray diffraction, allows us to determine the state of charge (SOC) of the individual particle. A continuous change in scattering intensity with SOC is also seen, enabling observation of a non-equilibrium kinetic phase separation within individual particles. Phase field modelling (informed by pulsed-field-gradient nuclear magnetic resonance and electrochemical experiments) is used to verify the kinetic origin of this separation, which arises from a dependence of the Li-ion diffusion coefficient upon SOC. Finally, we witness how such intra-particle SOC heterogeneity can lead to particle cracking; we follow the cycling behaviour of the resultant fragments, and show that they may become electrically disconnected from the electrode. These results demonstrate the power of optical scattering microscopy to track rapid non-equilibrium processes, often occurring over less than 1 minute, which would be inaccessible with established characterisation techniques.

Particle (ecology)

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A Quantization Procedure for Nonlinear Pricing with an Application to Electricity Markets

arXiv (Cornell University) (2023)

Quentin Jacquet Wim van Ackooij Clémence Alasseur Stéphane Gaubert

We consider a revenue maximization model, in which a company aims at designing a menu of contracts, given a population of customers. A standard approach consists in constructing an incentive-compatible continuum of contracts, i.e., a menu composed of an infinite number of contracts, where each contract is especially adapted to an infinitesimal customer, taking his type into account. Nonetheless, in many applications, the company is constrained to offering a limited number of contracts. We show that this question reduces to an optimal quantization problem, similar to the pruning problem that appeared in the max-plus based numerical methods in optimal control. We develop a new quantization algorithm, which, given an initial menu of contracts, iteratively prunes the less important contracts, to construct an implementable menu of the desired cardinality, while minimizing the revenue loss. We apply this algorithm to solve a pricing problem with price-elastic demand, originating from the electricity retail market. Numerical results show an improved performance by comparison with earlier pruning algorithms.

Nonlinear pricing

Pruning

10.48550/arxiv.2303.17394

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Expanding the Rich Crystal Chemistry of Ruthenium(V) Oxides via the Discovery of BaRu₂O₆, Ba₅Ru₄O₁₅, Ba₂Ru₃O₁₀, and Sr₂Ru₃O₉(OH) by pH-Controlled Hydrothermal Synthesis

Chemistry of Materials (2019)

Thomas Marchandier Quentin Jacquet Gwenaëlle Rousse Benoı̂t Baptiste Artem M. Abakumov

Along the years, ruthenium oxides have been deeply investigated for their magnetic or catalytic properties. The exploration of new synthesis processes, and especially low-temperature ones, is of primary importance to obtain new materials with interesting properties. Here, we highlight the tunability of a low-temperature (200 °C) hydrothermal synthesis route of alkaline-earth ruthenates. Changing only simple physicochemical parameters such as pH, it is possible to obtain a large diversity of metastable compounds. Among them, four compounds, namely, BaRu2O6, Ba2Ru3O10, Ba5Ru4O15, and Sr2Ru3O9(OH) are reported here for the first time. The influence of the reaction parameters (temperature, counter ions, reactant ratio, and pH) is studied. According to these observations, the importance of the reaction pH is highlighted and a reaction scenario is proposed. Finally, the crystal structures of Ba2Ru3O10, Ba5Ru4O15, and Sr2Ru3O9(OH) are reported. These findings further highlight the richness of low-temperature chemistry in the discovery of new metastable phases to be further explored by scientists.

Metastability

Crystal Chemistry

10.1021/acs.chemmater.9b02510

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Citations (8)

Mapping reaction mechanism during overcharge of a LiNiO2/Graphite-silicon lithium-ion battery: a correlative operando approach by simultaneous gas analysis and synchrotron scattering techniques

arXiv (Cornell University) (2024)

Quentin Jacquet Irina Profatilova Loïc Baggetto Bouthayna Alrifai Elisabeth Addes

Li-ion battery degradation processes are multi-scale, heterogeneous, dynamic and involve multiple cell components through cross talk mechanisms. Correlated operando characterization capable of measuring several key parameters are needed to accelerate understanding on these complex degradation processes. In particular, degradation mechanisms during overcharge of LiNiO2/Graphite-Silicon is well known at the material level featuring O2 gas release and concomitant surface reconstruction of LiNiO2. However, there are still debates regarding the role of high voltage O1 phase formation on gas production and no information on the effect of produced gases on the cell components (anode or sensors), or effect of overcharge on electrode level behavior. In this work, we simultaneously measured the gas produced using operando mass spectrometry while spatially resolving nanostructure and lattice changes using operando micro SAXS/WAXS mapping during the formation and over charge of a LiNiO2/Gr-Si pouch cell. This new correlated operando characterization experiment allowed to (1) confirm the absence of O1 phase even with substantial gas produced at end of charge, (2) unveil the effect of gases on reference and negative electrodes, (3) show that overcharge increases in-plane reaction heterogeneities by creating local degraded spots lagging behind the ensemble electrochemistry. These findings will be important to optimize ageing of devices based on similar chemistries, in particular Ni-rich NMC, while showing the strength of correlated characterization leading to more efficient and robust information on complex mechanisms.

Overcharge

10.48550/arxiv.2405.04931

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Phase Behavior during Electrochemical Cycling of Ni‐Rich Cathode Materials for Li‐Ion Batteries

Advanced Energy Materials (2020)

Chao Xu Philip J. Reeves Quentin Jacquet Clare P. Grey

Abstract Although layered lithium nickel‐rich oxides have become the state‐of‐the‐art cathode materials for lithium‐ion batteries in electric vehicle (EV) applications, they can suffer from rapid performance failure—particularly when operated under conditions of stress (temperature, high voltage)‐the underlying mechanisms of which are not fully understood. This essay aims to connect electrochemical performance with changes in structure during cycling. First, structural properties of LiNiO 2 are compared to the substituted Ni‐rich compounds NMCs (LiNi x Mn y Co 1− x − y O 2 ) and NCAs (LiNi x Co y Al 1− x − y O 2 ). Particular emphasis is placed on decoupling intrinsic behavior and extrinsic “two‐phase” reactions observed during initial cycles, as well as after extensive cycling for NMC and NCA cathodes. The need to revisit the various high‐voltage structural changes that occur in LiNiO 2 with modern characterization tools is highlighted to aid the understanding of the accelerated degradation for Ni‐rich cathodes at high voltages.

Decoupling (probability)

Cycling

10.1002/aenm.202003404

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Citations (260)