High-rate Battery Applications Research Articles

Mapping internal temperatures during high-rate battery applications.

Electric vehicles demand high charge and discharge rates creating potentially dangerous temperature rises. Lithium-ion cells are sealed during their manufacture, making internal temperatures challenging to probe1. Tracking current collector expansion using X-ray diffraction (XRD) permits non-destructive internal temperature measurements2; however, cylindrical cells are known to experience complex internal strain3,4. Here, we characterize the state of charge, mechanical strain and temperature within lithium-ion 18650 cells operated at high rates (above 3C) by means of two advanced synchrotron XRD methods: first, as entire cross-sectional temperature maps during open-circuit cooling and second, single-point temperatures during charge-discharge cycling. We observed that a 20-minute discharge on an energy-optimized cell (3.5 Ah) resulted in internal temperatures above 70 °C, whereas a faster 12-minute discharge on a power-optimized cell (1.5 Ah) resulted in substantially lower temperatures (below 50 °C). However, when comparing the two cells under the same electrical current, the peak temperatures were similar, for example, a 6 A discharge resulted in 40 °C peak temperatures for both cell types. We observe that the operando temperature rise is due to heat accumulation, strongly influenced by the charging protocol, for example, constant current and/or constant voltage; mechanisms that worsen with cycling because degradation increases the cell resistance. Design mitigations for temperature-related battery issues should now be explored using this new methodology to provide opportunities for improved thermal management during high-rate electric vehicle applications.

Toward a molecular understanding of the conductivity of lithium-ion conducting polyanion polymer electrolytes by molecular dynamics simulation.

With the improved lithium-ion transference number near unity, the low conductivity of single lithium-ion conducting solid polymer electrolytes (SLIC-SPEs) still hinders their application in high-rate batteries. Though some empirical conclusions on the conducting mechanism of SLIC-SPEs have been obtained, a more comprehensive study on the quantitative relationship between the molecular structure factors and ionic conduction performance is expected. In this study, a model structure that contains adjustable main chain and anion groups in the polyethylene oxide (PEO) matrix was used to clarify the influence of molecular structural factors on ionic conductivity and electrochemical stability of SLIC-SPEs. The anionic group was further disassembled into the intermediate group and end group while the main chain structure was distinguished into different degrees of polymerization and various lengths of the spacers between anions. Therefore, a well-defined molecular structure was employed to describe its relationship with ionic conductivity. In addition, the dissociation degree of salts and mobility of ions changing with the molecular structure were also discussed to explore the fundamental causes of conductivity. It can be concluded that the anion group affects the conductivity mainly via the dissociation degree, while the main chain structure impacts the conductivity by both dissociation degree and mobility.

Densely-stacked N-doped mesoporous TiO2/carbon microsphere derived from outdated milk as high-performance electrode material for energy storages

Spherical N-doped mesoporous TiO2/C (MTC) composite micro-particles are produced by spray drying (SD) and carbonization process. The particle size of MTC microsphere is between 2 and 3.4 µm, and the N-doped amorphous C around TiO2 could provide a conductive matrix, and buffer the volume change. When evaluated as electrodes for Li-ion batteries (LIBs) and Li-S batteries (LSBs), the MTC microsphere exhibits relatively high discharge-voltage plateau, excellent capacity retention and rate capability. As anode for LIBs, after 200 cycles, a reversible capacity more than 230 mA h g−1 can achieved at 1 C. And for LSBs, a specific capacity of 1317.7 mA h g−1 at 1 C and the capacity retention of 73.8% after 500 cycles. The superior electrochemical performance is ascribed to robust scaffolding architecture and conductive N-doped carbon matrix. The excellent electrochemical performance and process ability of the MTC microspheres make them very attractive as electrode materials for use in high rate battery application.

Lithium Titanate Confined in Nanoporous Copper for High-Rate Battery Applications

ABSTRACTDue to extremely high conductivity of copper (Cu), copper–based nanocomposites offer remarkable opportunities for use in energy conversion and storage. Their applications demand low-cost syntheses routes relying on using inexpensive equipment with no formation of hazardous wastes. In this work, we report on a novel, cheap and environmentally friendly synthesis and application of nano-porous Cu as a support for lithium titanate. The infiltration of lithium titanate onto the inner surface of NPCu produced high-rate anodes for Li-ion batteries capable of providing nearly 50mAh/g during about 20s charging while retaining about 70% of the initial capacity after 1000 charge-discharge cycles. The demonstrated versatility and simplicity of this fascinating approach show great promises for scalable production and the use of NPCu in various cost-sensitive applications.

Self-supporting hierarchical rGO@Ni nanosheet@Co3O4 nanowire array and its application in high-rate batteries

Abstract To meet the design requirements for high-rate battery electrodes, self-supporting hierarchical rGO@Ni nanosheet@Co3O4 nanowire array film with light weight is synthesized via a series of controllable fabrication processes. Due to modifying the highly conductive nickel nanosheets onto the surface of rGO film, the energy storage performance of this hybrid film is enhanced, especially in rate capability. The whole high-rate battery, which is fabricated by using this film as the positive electrode, manifests the maximum energy density of 20.3 Wh kg−1 at a power density of 326 W kg−1 along with excellent capacity retention of 81.4% after 5000 cycles. Therefore, the rGO-Ni-Co3O4 hybrid film is a promising electrode material for flexible long-life cycling high-rate batteries.

Self-supported, binder-free 3D hierarchical iron fluoride flower-like array as high power cathode material for lithium batteries

We present a tactful and advanced architecture design of self-supported, binder-free 3D hierarchical iron fluoride flower-like array directly growing on Ti foil by a solvothermal approach. The probable growth mechanism of the 3D microflower is explored. The advantages of the porous 3D hierarchical nanostructure materials endow a stable capacity of 123mAhg−1 at 3C rate, and a good rate capability of 101mAhg−1 at a high current density of 2Ag−1 (10C). The superior electrochemical performance can be ascribed to the synergistic effect of charge transfer expressway, high specific surface area and porous hierarchical structure for electrolyte penetration deriving from the unique porous 3D hierarchical structure. The superior electrochemical performance combined with the unique structure of the FeF3·0.33H2O flower-like array demonstrates its great potential of being utilized as the cathode material in high rate battery application.

Fabrication of high tap density LiFe0.6Mn0.4PO4/C microspheres by a double carbon coating–spray drying method for high rate lithium ion batteries

Spherical LiFe0.6Mn0.4PO4/C particles with high tap density were successfully synthesized by sintering spherical precursor powders prepared by a modified spray drying method with a double carbon coating process. The obtained secondary spheres were made of carbon-coated nanocrystallines (∼100 nm), exhibiting a high tap density of 1.4 g cm−3. The LiFe0.6Mn0.4PO4/C microspheres had a reversible capacity of 160.2 mAh g−1 at 0.1C, and a volume energy density of 801.5 Wh L−1 which is nearly 1.4 times that of their nano-sized counterparts. This spherical material showed remarkable rate capability by maintaining 106.3 mAh g−1 at 20C, as well as excellent cycleablity with 98.9% capacity retention after 100 cycles at 2C and 200 cycles at 5C. The excellent electrochemical performance and processability of the LiFe0.6Mn0.4PO4/C microspheres make them very attractive as cathode materials for use in high rate battery application.

Ni–Mn hydroxides as new high power electrode materials for supercapacitor applications

The coprecipitation of Ni and Mn hydroxides followed by freeze drying results in the formation of agglomerated 20–30 nm particles of complex hydroxide with spinel-like structure. The thermal decomposition of this hydroxide causes the formation of ilmenite-type complex oxide at T > 300 °C without considerable changes in the Ni and Mn valence states according to X-ray photoelectron spectroscopy data. Further processing at T ≤ 400 °C is accompanied by significant particle intergrowth though their internal structure remains nanostructured. Ni–Mn oxide- and hydroxide-based electrodes revealed a significant reversible electrochemical activity in the alkaline electrolytes and an extended operating voltage window (~ 1.8 V). Ni–Mn ilmenite-based electrode materials demonstrated a low fade rate and high specific electrochemical capacity values at high discharge rates (up to 70 mAh g − 1 at I = 70 mA cm − 2 ) that makes feasible their application in high rate batteries and electrochemical supercapacitors.