Chao-Yang Wang

Solid‐state batteries (SSBs) hold immense potential for improved energy density and safety compared to traditional batteries. However, existing solid‐state electrolytes (SSEs) face challenges in meeting the complex operational requirements of SSBs. This study introduces a novel approach to address this issue by developing a metal‐organic framework (MOF) with customized bilayer zwitterionic nanochannels (MOF‐BZN) as high‐performance SSEs. The BZN consist of a rigid anionic MOF channel with chemically grafted soft multicationic oligomers (MCOs) on the pore wall. This design enables selective superionic conduction, with MCOs restricting the movement of anions while coulombic interaction between MCOs and anionic framework promoting the dissociation of Li+. MOF‐BZN exhibits remarkable Li+ conductivity (8.76 × 10−4 S cm−1), high Li+ transference number (0.75), and a wide electrochemical …

Thermal management is critical for safety, performance, and durability of lithium-ion batteries that are ubiquitous in consumer electronics, electric vehicles (EVs), aerospace, and grid-scale energy storage. Toward mass adoption of EVs globally, lithium-ion batteries are increasingly used under extreme conditions including low temperatures, high temperatures, and fast charging. Furthermore, EV fires caused by battery thermal runaway have become a major hurdle to the wide adoption of EVs. These extreme conditions pose great challenges for thermal management and require unconventional strategies. The interactions between thermal, electrochemical, materials, and structural characteristics of batteries further complicate the challenges, but they also enable opportunities for developing innovative strategies of thermal management. In this review, the challenges for thermal management under extreme …

Lithium-ion batteries with nickel-rich layered oxide cathodes and graphite anodes have reached specific energies of 250–300 Wh kg−1 (refs. ,), and it is now possible to build a 90 kWh electric vehicle (EV) pack with a 300-mile cruise range. Unfortunately, using such massive batteries to alleviate range anxiety is ineffective for mainstream EV adoption owing to the limited raw resource supply and prohibitively high cost. Ten-minute fast charging enables downsizing of EV batteries for both affordability and sustainability, without causing range anxiety. However, fast charging of energy-dense batteries (more than 250 Wh kg−1 or higher than 4 mAh cm−2) remains a great challenge,. Here we combine a material-agnostic approach based on asymmetric temperature modulation with a thermally stable dual-salt electrolyte to achieve charging of a 265 Wh kg−1 battery to 75% (or 70%) state of charge in 12 (or 11 …

The transition toward electrified mobility is rapidly accelerating, but sustainability challenges associated with batteries, including costs, raw materials, and manufacturing-related emissions, pose barriers. Here, we discuss the role of extreme fast charging in breaking down these barriers and offering a pathway toward a more sustainable battery-powered electric-vehicle market.

In this study, a high fuel utilization approach for polymer electrolyte fuel cells (PEFC) is proposed and studied experimentally. This approach uses an ultra-low hydrogen stoichiometry supply (i.e., ξa = 1.02) meanwhile sustaining stable cell performance. Systematic experiments showed the feasibility of high fuel utilization approach under different pressures and hydrogen/air inlet humidification conditions. It is indicated that the fuel cell is able to provide stable performance at a real fuel stoichiometry ξa = 1.02 under high-current density operation. For all the tests at ξa/ξc = 1.5/2.0 or 1.02/2.0, there exist unstable operation regimes typically in low power conditions. The instability as a result of flooding is affected mainly by air stoichiometry and less by fuel stoichiometry.

To break away from the trilemma among safety, energy density, and lifetime, we present a new perspective on battery thermal management and safety for electric vehicles. We give a quantitative analysis of the fundamental principles governing each and identify high-temperature battery operation and heat-resistant materials as important directions for future battery research and development to improve safety, reduce degradation, and simplify thermal management systems. We find that heat-resistant batteries are indispensable toward resistance to thermal runaway and therefore ultimately battery safety. Concurrently, heat-resistant batteries give rise to long calendar life when idling at ambient temperatures and greatly simplify thermal management while working, owing to much enlarged temperature difference driving cooling. The fundamentals illustrated here reveal an unconventional approach to the development …

Electric vertical takeoff and landing (eVTOL) aircraft have attracted considerable interest as a disruptive technology to transform future transportation systems. Their unique operating profiles and requirements present grand challenges to batteries. This work identifies the primary battery requirements for eVTOL in terms of specific energy and power, fast charging, cycle life, and safety, revealing that eVTOL batteries have more stringent requirements than electric vehicle batteries in all aspects. Notably, we find that fast charging is essential for downsizing aircraft and batteries for low cost while achieving high vehicle utilization rates to maximize revenues. We experimentally demonstrate two energy-dense Li-ion battery designs that can recharge adequate energy for 80 km eVTOL trips in 5–10 min and sustain over 2,000 fast-charge cycles, laying a foundation for eVTOL batteries.

Battery thermal management systems (BTMSs) are expected to keep the battery temperature at a moderate level (∼30 °C) to minimize the thermally exacerbated degradation. However, during fast charging, a strong cooling system is required to restrict the temperature rise of Li-ion batteries (LiBs), which significantly increases the cost and weight of battery packs, and induces a large temperature variation inside the battery. In this work we find that all these drawbacks could be relieved by allowing LiBs to charge at higher temperatures. Since the fast charging of a LiB only takes a tiny fraction of its lifetime, the aging rate is limited even at a charging temperature of 60 °C. Three types of thermal environments are proposed: kept constant at 30 °C, preheated to 60 °C, and adiabatic fast charging. With an experimentally validated electrochemical-thermal (ECT) coupled model, we explore the interplay between thermal …

The pursuit of energy density has driven electric vehicle (EV) batteries from using lithium iron phosphate (LFP) cathodes in early days to ternary layered oxides increasingly rich in nickel; however, it is impossible to forgo the LFP battery due to its unsurpassed safety, as well as its low cost and cobalt-free nature. Here we demonstrate a thermally modulated LFP battery to offer an adequate cruise range per charge that is extendable by 10 min recharge in all climates, essentially guaranteeing EVs that are free of range anxiety. Such a thermally modulated LFP battery designed to operate at a working temperature around 60 °C in any ambient condition promises to be a well-rounded powertrain for mass-market EVs. Furthermore, we reveal that the limited working time at the high temperature presents an opportunity to use graphite of low surface areas, thereby prospectively prolonging the EV lifespan to greater than …

We demonstrate that an energy-dense, 288 Wh kg−1 lithium-ion battery can provide 152 Wh kg−1 energy and 1056 W kg−1 power at ultralow temperatures such as −40 or −50 °C, contrary to virtually no performance expected under two simultaneous extremes: 4.04 mAh cm−2 cathode loading and −40 °C. Unleashing this huge potential of current battery materials is achieved through a self-heating structure by embedding a micron-thin nickel foil in the electrochemical energy storage cell. The heating process from −40 to 10 °C consumes only 5.1% of battery energy and takes 77 s. Further, based on the chemistry agnostic nature of self-heating, we present a generic chart to transform rate capability of lithium-ion and lithium metal batteries. These illustrative examples point to a new era of battery structure innovation, significantly broadening the performance envelopes of existing and emerging battery materials for …

High-nickel layered oxide Li-ion batteries (LIBs) dominate the electric vehicle market, but their potentially poor safety and thermal stability remain a public concern. Here, we show that an ultrahigh-energy LIB (292 Wh kg−1) becomes intrinsically safer when a small amount of triallyl phosphate (TAP) is added to standard electrolytes. TAP passivates the electrode-electrolyte interfaces and limits the maximum cell temperature during nail penetration to 55°C versus complete cell destruction (>950°C) without TAP. The downside of this reliable safety solution is higher interfacial impedance and hence lower battery power; however, thermal modulation for battery operation around 60°C can restore power completely. When cycled at 60°C, the cell stabilized with TAP achieved 2,413 cycles at 76% capacity retention. Such an unconventional combination of interface-passivating electrolyte additive with cell thermal modulation …

In this paper, ultrahigh fuel utilization (>98%) in polymer electrolyte fuel cells (PEFCs) is numerically studied to investigate three aspects for this operation strategy: its effect on fuel cell performance, occurance of fuel starvation, and altered water management. Simulation results reveal that the anode flow, when using pure hydrogen fuel, decelerates to nearly zero under the high fuel utlization. The anode gas flow remains high in the hydrogen concentration throughout the gas flow channel, eliminating concerns of fuel starvation and increased anode overpotential. The numerical study confirms the experimental observation that the high-fuel-utilization strategy has very little impact on cell power output in the stable operating regime. It is shown that fuel cell’s water removal almost totally relies on the cathode channel flow under ultrahigh fuel utilization, which may be one cause for experimentally observed instability in …

Li metal batteries (LMBs) employing high voltage cathodes show promise as next generation batteries for electric vehicles due to their high energy density. However, the cycling stability of such energy-dense LMBs at high charge rates has seldom been explored. In this work, Li Coulombic efficiency (CE) as a function of current density (ie, C-rate) and temperature was investigated in ether-based highly concentrated electrolytes (HCEs). We found that Li metal anodes can be stably cycled in the HCEs at elevated temperatures with a high Li CE of> 99.4% for a plating capacity of 3 mAh cm− 2 at a high C-rate greater than 1 C. The cycling stability of LMB full cells with Li (Ni 0.8 Co 0.1 Mn 0.1) O 2 (NMC811) cathodes was also investigated at different charge rates (1 C to 3 C) at 40 and 60 C. The LMBs with high areal capacity (∼ 3.2 mAh cm− 2) NMC811 cathodes and minimal Li excess anodes (negative/positive …

Estimation of heat generation in lithium-ion batteries (LiBs) is critical for enhancing battery performance and safety. Here, we present a method for estimating total heat generation in LiBs based on dual-temperature measurement (DTM) and a two-state thermal model, which is both accurate and fast for online applications. We demonstrate that the algorithm can keep track of the heat generation rate in real-time under scenarios of designed multi-stepwise heat generation profile and regular fast charging processes. Moreover, the algorithm requires no knowledge of the thermal boundary conditions, providing robustness against changes in convection conditions and ambient temperatures. Finally, this method can capture heat generation induced by abnormal exothermic reactions, which could be a useful tool for detection of battery thermal failures.

Li metal batteries (LMBs) employing high voltage cathodes are necessary to attain high energy density. Although highly concentrated ether-based electrolytes (eg 4 M LiFSI/DME) can yield stable cycling of Li metal anodes, their high voltage instability fosters incompatibility with high voltage cathodes. In this work, the temperature dependence of fresh cell performance, Li Coulombic efficiency (CE), and cycling stability of LMBs in highly concentrated LiFSI/DME electrolytes was explored. Elevated temperature operation was deemed essential for highly concentrated electrolytes to achieve practical rate capability. Moreover, at 60 C, the cycling stability of Li metal anodes with a Li CE as high as 99.2% was demonstrated in a highly concentrated LiFSI-1.2 DME electrolyte (LiFSI: DME= 1: 1.2 mol.). At room temperature, the LiFSI-1.2 DME electrolyte enabled stable LMBs with NMC622 cathodes. However, due to the high …

Provided is an all solid-state lithium battery including solid battery materials and whose ohmic resistance is modulated according to temperature. The all solid-state lithium battery can include a solid electrolyte; at least two terminals for operating the battery at one level of internal resistance (R1) over a temperature range of the battery between a first temperature (T1) and a second temperature (T2); at least one high resistance terminal for operating the battery at a second level of internal resistance (R2) outside of either T1 or T2; and a switch that activates R2 when the temperature of the battery is outside of either T1 or T2. The battery can be configured to include at least one resistor sheet embedded within a cell of the battery and electrically connected to the at least one high resistance terminal.

We present a novel concept to achieve high performance and high safety simultaneously by passivating a Li-ion cell and then self-heating before use. By adding a small amount of triallyl phosphate in conventional electrolytes, we show that resistances of the passivated cells can increase by ~5×, thereby ensuring high safety and thermal stability. High power before battery operation is delivered by self-heating to an elevated temperature such as 60°C within tens of seconds. The present approach of building a resistive cell with highly stable materials and then delivering high power on demand through rapid thermal stimulation leads to a revolutionary route to high safety when batteries are not in use and high battery performance upon operation.