Enabling Stable Operation of Lithium-Ion Batteries under Fast-Operating Conditions by Tuning the Electrolyte Chemistry

Removing α-H in Carboxylate-Based Electrolytes for Stable Lithium Metal Batteries

Although carboxylate esters greatly improve the cold weather performance of graphite-based lithium-ion batteries utilized in arctic expeditions, the underlying cause of the incompatibility between carboxylates and lithium (Li) anodes has not been sufficiently explained, resulting in the greatly restricted usage of carboxylate in lithium metal batteries (LMBs). Herein, we reveal the serious parasitic reactions between carboxylate α-H atoms and Li metal are the culprits that render carboxylate-based ineffectiveness for LMBs. By replacing all α-H atoms with fluorine atoms and methyl groups, we successfully construct inert carboxylates and find the ions/molecules distribution in electric-double-layer (EDL) can be manipulated at a molecular-level. The unique structure ensuring more anions are positioned closer to the Li surface in the EDL of the inert carboxylate-based electrolyte, the morphology of the deposited Li is significantly regulated and the chemical corrosion gets effectively inhibited, as a consequence of remarkable extending lifespan of carboxylate-based LMBs with routine salt concentration and few additives. More generally, using carboxylates lacking α-H atoms offer a realistic approach to increase the variety of solvents that can be used in LMBs electrolytes.

Realizing a 3 C Fast-Charging Practical Sodium Pouch Cell

Sodium-ion batteries (SIBs), endowed with relatively small Stokes radius and low desolvation energy of Na+, are reckoned as a promising candidate for fast-charging endeavors. However, the C-rate charging capability of practical energy-dense sodium-ion pouch cells is currently limited to ≤1 C, due to the high propensity for detrimental metallic Na plating on the hard carbon (HC) anode at elevated rates. Here, an ampere-hour-level sodium-ion pouch cell capable of 3 C charging is successfully developed via phosphorus (P)-sulfur (S) interphase chemistry. By rational electrolyte regulation, desired P-S constituents, namely, Na3PO4 and Na2SO4, are generated in the solid-electrolyte interphase with favorable Na+ interface kinetics. Specifically, Na+ desolvation energy barrier has been greatly lowered by the weak ion-solvent coordination near the inner Helmholtz plane on Na3PO4 interphase, while Na2SO4 expedites charge carrier mobility due to its intrinsically high ionic conductivity. Consequently, an energy-dense (126 Wh kg-1) O3-Na(Ni1/3Fe1/3Mn1/3)O2||HC pouch cell capable of 3 C charging (100 % state of charge) without Na plating can be achieved, with a great capacity retention of 91.5 % over 200 cycles. Further, the assembled power-type Na3V2(PO4)3||HC pouch cell displays an impressive fast-charging capability of 50 C, which surpasses that of previously reported high-power SIBs. This work serves as an enlightenment for developing fast-charging SIBs.

A Perspective on Pathways Toward Commercial Sodium-Ion Batteries

Lithium-ion batteries (LIBs) have been widely adopted in the automotive industry, with an annual global production exceeding 1000 GWh. Despite their success, the escalating demand for LIBs has created concerns on supply chain issues related to key elements, such as lithium, cobalt, and nickel. Sodium-ion batteries (SIBs) are emerging as a promising alternative due to the high abundance and low cost of sodium and other raw materials. Nevertheless, the commercialization of SIBs, particularly for grid storage and automotive applications, faces significant hurdles. This perspective article aims to identify the critical challenges in making SIBs viable from both chemical and techno-economic perspectives. First, a brief comparison of the materials chemistry, working mechanisms, and cost between mainstream LIB systems and prospective SIB systems is provided. The intrinsic challenges of SIBs regarding storage stability, capacity utilization, cycle stability, calendar life, and safe operation of cathode, electrolyte, and anode materials are discussed. Furthermore, issues related to the scalability of material production, materials engineering feasibility, and energy-dense electrode design and fabrication are illustrated. Finally, promising pathways are listed and discussed toward achieving high-energy-density, stable, cost-effective SIBs.

Multi-dimensional, Multi-scale Analysis of Interphase Chemistry for Enhanced Fast-Charging of Lithium-Ion Batteries with Ion Mass Spectrometry

Understanding the fundamental properties of electrode-electrolyte interphases (EEIs) is essential for designing electrolytes that support stable operation under high charging rates. In this study, we benchmark our fast-charging electrolyte (FCE) against the commercial LP57 electrolyte to identify the EEI characteristics that enhance fast-charging performance. By utilizing the latest advances in time-of-flight secondary ion mass spectrometry (TOF-SIMS) and focused-ion beam (FIB) techniques, we reveal the complex chemical architecture of the cathode-electrolyte interphase (CEI). Our findings indicate that stable battery operation under fast-charging conditions requires reduced surface reactivity rather than stabilizing the bulk integrity of the cathode. While inorganic species are often cited as beneficial for EEI composition, their distribution within the EEI is equally critical. Additionally, dynamic interactions between the cathode material and conductive carbon significantly affect CEI formation and alter the passivation layer chemistry. A chemically homogeneous distribution of CEI components passivating preferentially the active material particles is desired for enhanced performance. Notably, the amount of electrolyte decomposition species in the solid-electrolyte interphase (SEI) far outweighs their distribution within the SEI in determining better electrochemical performance. An inorganic-rich SEI effectively protects graphite particles, suppresses the accumulation of metallic lithium, and prevents the formation of lithium dendrites. Overall, an enhanced fast-charging performance can be achieved by tuning the interphase chemistry and architecture on both the cathode and anode sides.

Ultrafast Lithium-Ion Transport Engineered by Nanoconfinement Effect

Amid the burgeoning demand for electrochemical energy storage and neuromorphic computing, fast ion transport behavior has attracted widespread attention at both fundamental and practical levels. Here, based on the nanoconfined channel of graphene oxide laminar membranes (GOLMs), the lithium ionic conductivity typically exceeding 102 mS cm-1 is realized, one to three orders of magnitude higher than traditional liquid or solid lithium-ion electrolyte. Specifically, the nanoconfined lithium hexafluorophosphate (LiPF6)-ethylene carbonate (EC)/ dimethyl carbonate (DMC) electrolyte demonstrates the ionic conductivity of 170 mS cm-1, outperforming the bulk counterpart by ≈16 fold. At the ultralow temperature of -60 °C, the nanoconfined electrolyte also maintains a practically useful conductivity of 11 mS cm-1. Furthermore, the in situ experimental and theoretical framework enables to attribute the enhanced ionic conductivity to the layer-by-layer cations and anions distribution induced by high surface charge and nanoconfinement effects in GO nanochannels. More importantly, integrating such rapid lithium-ion transport nanochannel into the LiFePO4 (LFP) cathode significantly improves the high-rate and long-cycle performance of lithium batteries. These results exhibit the convention-breaking ionic conductivity of nanoconfined electrolytes, inspiring the development of ultrafast ion diffusion pathways based on 2D nanoconfined channels for efficient energy storage applications.