The Development of Li Batteries
Authors: Liu Jia , Sun Liqun , Xie Haiming 
Published: February 2020

For effective use of renewable energy it must be coupled to energy storage devices with high efficiencies. One such technology is a battery, where the stored chemical energy can be converted into the electrical energy through the electrochemical reactions. We started the Li battery studies since 2002. Currently, our research covers the Li-ion batteries, Li-S batteries, Li-O2 batteries, and all-solid-state batteries. Here, I will present some results relating to the electrode materials, electrolyte, and electrode achitectures in our group.

We reported the Li-ion battery based on LiFePO4 cathode, which exhibits a good cyclability of 5,000 cycles and a considerable capacity retation of 90 % at -40℃. This novel type battery has been industied and applied for electric vehicles in the low temperature region. The NMC ternary battery and high-voltage battery based on LiNi0.5Mn1.5O2 are also introduced. Besides the cathode, some promising results relating to the anode part will be also introduced, including the graphene and VPO4/rGO. For Li-S battery, we firstly present a novel cathode of Mo2C nanorods-S composite, which exhibits a much lower capacity decay of 0.058 % per cycle at 2 C over 500 cycles. Additionally, the carbon-based separator decorated by red phsphorus nanoparticles for Li-S battery will be also introduced, which displays a good rate performance and a considerable cyclability of 500 cycles with 730 mAh/g. For Li-O2 battery, we reported the yolk-shell Co2CrO4 nanospheres as highly active catalysts. Based on the experimental results and DFT calculations, a direct evidence of Co2CrO4 employment being linked to the Li2O2 morphology was firstly provided and a catalytic mechanism was proposed. In addition, a 3D foam-like composite composing of Mo2C nanorods decorated by different amount of N-doped carbon was directly employed as the O2 electrode without applications of any binder and current collector. The fundamental information about the key factors and steps involved in the Li2O2 formation and decomposition was revealed. We will also introduce a flexible, self-standing, and binder-free O2 electrode by growing the flower-like MoS2 microspheres with sulfur deficiencies onto the CTs (Def-MoS2@CTs). Futhermore, I will introduce a novel electrolyte of a binary mixtures of highly concentrated tetraglyme electrolyte (HCG4) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) for the Li-O2 battery, which exhibits good wettability, enhanced ionic conductivity, considerable non-flammability, and high electrochemical stability. For all-solid-state battery, we will introduce a solid polyer electrolyte based on poly(ethylene oxide), which shows a superior electrochemical property with a decent lithium transference number of 0.35, a wide electrochemical stability window above 5 V vs. Li+/Li, and a low interfacial resistance. In addition, a triblock copolymer polystyrene-poly (ethylene glycol)-polystyrene (PS-PEG-PS) as the polymer electrolyte for all-solid-state battery will be also introduced, which displays a highly electrochemical stability and a considerable cyclability. Besides some fundermental results, I would like to introduce some industry-level developments in our pilot-line of batteries, because we cooperated with some enterprises of electric vehicles in China since 2009.

I would like to apply an oral presentation if possible. Thanks for your consideration.

Figure 1