Engineering topics

Niu, Chaojiang

Publications and source records attributed to Niu, Chaojiang.

23 records · Page 2

DOE OSTI2019

Good Practice for Safe Handling of Lithium Metal Anode and High Energy Rechargeable Lithium Metal Batteries

High-energy rechargeable lithium metal batteries have been intensively revisited in recent years. Since more researchers started to use pouch cell as the platform to study the fundamentals at relevant scales, safe testing and handling of lithium metal and high-energy lithium metal batteries have become critical. Cautions and safety procedures are needed when handling cycled pouch cells with pulverized lithium particles inside. From cell design, electrode preparation, cell fabrication to testing procedure, this work aims to discuss all possible root causes that may initiate cell internal shorting and raise safety concerns. Safe transfer and disposal of cycled pouch cells are also discussed. The insights provided in this article are applicable for the research on high-energy lithium-ion batteries as well and may inspire more safety strategies to accelerate research innovation by using large-format batteries as the testing vehicle and conduct the research safely.

25 ENERGY STORAGE↗

DOE OSTI2019

Nonflammable Electrolytes for Lithium Ion Batteries Enabled by Ultraconformal Passivation Interphases

Occasional fire accidents and continuous battery safety concerns require advanced lithium ion batteries (LIBs) with high safety as well as great battery performances. The electrolyte plays a critical role in electrochemical and safety properties. Organic phosphate solvents next to the state-of-the-art organic carbonates could formulate nonflammable electrolytes and intrinsically eliminate fire hazards, but their poor compatibility with the graphite anodes remains an obstacle for practical applications. This work reports a promising approach by formulating localized high concentration electrolytes based on a phosphate solvent, ethylene carbonate and a partially fluorinated ether. This electrolyte readily generates robust solid electrolyte interphase on graphite anode and cathode electrolyte interphase on LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode. As a result, this electrolyte shows good compatibility with high voltage cathode and graphite anode, and enables long-term cycling stability in graphite||NMC811 cells. This work sheds a new light in development of nonflammable electrolytes for high energy-density LIBs.

Non-flammable electrolyte, lithium ion battery, lo↗

DOE OSTI2019

Monolithic solid–electrolyte interphases formed in fluorinated orthoformate-based electrolytes minimize Li depletion and pulverization

Lithium (Li) pulverization and associated large volume expansion during cycling is one of the most critical barriers for the safe operation of Li-metal batteries. Here, we report an approach to minimize the Li pulverization using an electrolyte based on a fluorinated orthoformate solvent. The solid–electrolyte interphase (SEI) formed in this electrolyte clearly exhibits a monolithic feature, which is in sharp contrast with the widely reported mosaic- or multilayer-type SEIs that are not homogeneous and could lead to uneven Li stripping/plating and fast Li and electrolyte depletion over cycling. The highly homogeneous and amorphous SEI not only prevents dendritic Li formation, but also minimizes Li loss and volumetric expansion. Furthermore, this new electrolyte strongly suppresses the phase transformation of the LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode (from layered structure to rock salt) and stabilizes its structure. In conclusion, tests of high-voltage Li||NMC811 cells show long-term cycling stability and high rate capability, as well as reduced safety concerns.

25 ENERGY STORAGE↗

DOE OSTI2019

Enabling High-Voltage Lithium-Metal Batteries under Practical Conditions

Rechargeable lithium (Li) metal batteries (LMBs) offer a great opportunity for applications needing high-energy-density battery systems. However, rare progress has been demonstrated so far under practical conditions including high voltage, high loading cathode, thin Li anode, and lean electrolyte. Here, in opposite to the common wisdom, we report an ether-based localized high concentration electrolyte that can greatly enhance the stability of Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode under 4.4 V and 4.5 V with an effective protection interphase enriched in LiF. This effect, in combination with the superior Li stability in this electrolyte, enables dramatically improved cycling performances of Li||NMC811 batteries under highly challenging conditions. The LMBs can retain over 80% capacity in 150 stable cycles with extremely limited amounts of Li anode and electrolyte. The findings in this work point out a very promising strategy to develop practical high-energy LMBs.

Ren, Xiaodi↗

DOE OSTI2019

High-energy lithium metal pouch cells with limited anode swelling and long stable cycles

Li metal anode has attracted wide attentions for high-energy cells, but there have been few reports of long term cycling and the degradation mechanism of realistic high-energy Li metal batteries (LMBs). A key issue inherent to high-energy LMBs is cell swelling due to continuous side reactions between Li and electrolyte. Herein, a prototypical 300 Wh kg-1 (1.0 Ah) pouch cell is developed by combining Li metal anode and LiNi0.6Mn0.2Co0.2O2 cathode. In a conventional carbonate electrolyte, the cell can only last 12 cycles because of the depletion of Li and electrolyte accompanied by a serious cell swelling of more than 110% thickening. Through the integration of a new compatible electrolyte and a uniform external pressure, over 200 stable cycles with 86% capacity retention and 83% energy retention have been demonstrated. Using this 300 Wh kg-1 pouch cell as a platform, two continuous but different Li anode structural evolution processes are revealed: (1) in the initial 50 cycles, flat Li foil converts into large Li particles entangled within the solid electrolyte interphase (SEI) layer, leading to a fast anode volume expansion and cell thickening. (2) As cycling continued, the external pressure maintains good contact between Li particles to ensure a percolation pathway for both ions and electrons thus the electrochemical reactions continue to occur through the entire anode. The individual solid Li particles evolve into a porous structure buffering the further anode volume expansion. Accordingly, Li anode thickening is significantly reduced with only 19% cell swelling in subsequent 150 cycles.

Niu, Chaojiang↗