Electrolyte Engineering Toward High Performance High Nickel (Ni ≥ 80%) Lithium-Ion Batteries

Nano-Enhanced Graphite/Phase Change Material/Graphene Composite for Sustainable and Efficient Passive Thermal Management

Passive battery thermal management systems (BTMSs) are critical for mitigation of battery thermal runaway (TR). Phase change materials (PCMs) have shown promise for mitigating transient thermal challenges. Fluid leakage and low effective thermal conductivity limit PCM adoption. Furthermore, the thermal capacitance of PCMs diminishes as their latent load is exhausted, creating an unsustainable cooling effect that is transitory. Here, an expanded graphite/PCM/graphene composite that solves these challenges is proposed. The expanded graphite/PCM phase change composite eliminates leakage and increases effective thermal conductivity while the graphene coating enables radiative cooling for PCM regeneration. The composite demonstrates excellent thermal performance in a real BTMS and shows a 26% decrease in temperature when compared to conventional BTMS materials. The composite exhibits thermal control performance comparable with active cooling, resulting in reduced cost and increased simplicity. In addition to BTMSs, this material is anticipated to have application in a plethora of engineered systems requiring stringent thermal management.

An Electrode-Crosstalk-Suppressing Smart Polymer Electrolyte for High Safety Lithium-Ion Batteries

Electrode crosstalk between anode and cathode at elevated temperatures is identified as a real culprit triggering the thermal runaway of lithium-ion batteries. Herein, to address this challenge, a novel smart polymer electrolyte is prepared through in situ polymerization of methyl methacrylate and acrylic anhydride monomers within a succinonitrile-based dual-anion deep eutectic solvent. Owing to the abundant active unsaturated double bonds on the as-obtained polymer matrix end, this smart polymer electrolyte can spontaneously form a dense crosslinked polymer network under elevated temperatures, effectively slowing down the crosstalk diffusion kinetics of lithium ions and active gases. Impressively, LiCoO2/graphite pouch cells employing this smart polymer electrolyte demonstrate no thermal runaway even at the temperature up to 250 °C via accelerating rate calorimeter testing. Meanwhile, because of its abundance of functional motifs, this smart polymer electrolyte can facilitate the formation of stable and thermally robust electrode/electrolyte interface on both electrodes, ensuring the long cycle life and high safety of LIBs. In specific, this smart polymer electrolyte endows 1.1 Ah LiCoO2/graphite pouch cell with a capacity retention of 96% after 398 cycles at 0.2 C.

Failure of Lithium-Ion Batteries Accelerated by Gravity

The safety concerns surrounding lithium-ion batteries (LIBs) have garnered increasing attention due to their potential to endanger lives and incur significant financial losses. However, the origins of battery failures are diverse, presenting significant challenges in developing safety measures to mitigate accidental catastrophes. In this study, the aging mechanism of LiNi0.5Co0.2Mn0.3O2||graphite-based cylindrical 18,650 LIBs stored at room temperature for two years was investigated. It was found that an uneven distribution of electrolytes can be caused by gravity, leading to temperature variations within the battery. Specifically, it was observed that the temperature at the top of the battery was approximately -0.89 °C higher than at the bottom, correlating with an increase in partial internal resistance. Additionally, upon disassembly and analysis of spent batteries, the most significant damage to electrode materials at the top of the battery was observed. These findings suggest that gravity-induced electrolyte insufficiency exacerbates side reactions, particularly at the top of the battery. This study offers a unique perspective on the safety concerns associated with high-energy-density batteries in long-term and large-scale applications.

Interphase Regulation by Multifunctional Additive Empowering High Energy Lithium-Ion Batteries with Enhanced Cycle Life and Thermal Safety

High energy density lithium-ion batteries (LIBs) adopting high-nickel layered oxide cathodes and silicon-based composite anodes always suffer from unsatisfied cycle life and poor safety performance, especially at elevated temperatures. Electrode /electrolyte interphase regulation by functional additives is one of the most economic and efficacious strategies to overcome this shortcoming. Herein, cyano-groups (-CN) are introduced into lithium fluorinated phosphate to synthesize a novel multifunctional additive of lithium tetrafluoro (1,2-dihydroxyethane-1,1,2,2-tetracarbonitrile) phosphate (LiTFTCP), which endows high nickel LiNi0.8 Co0.1 Mn0.1 O2 /SiOx -graphite composite full cell with an ultrahigh cycle life and superior safety characteristics, by adding only 0.5 wt % LiTFTCP into a LiPF6 -carbonate baseline electrolyte. It is revealed that LiTFTCP additive effectively suppresses the HF generation and facilitates the formation of a robust and heat-resistant cyano-enriched CEI layer as well as a stable LiF-enriched SEI layer. The favorable SEI/CEI layers greatly lessen the electrode degradation, electrolyte consumption, thermal-induced gassing and total heat-releasing. This work illuminates the importance of additive molecular engineering and interphase regulation in simultaneously promoting the cycling and thermal safety of LIBs with high-nickel NCMxyz cathode and silicon-based composite anode.