New insight of stabilizing electrode/electrolyte interphase:Regulating the specific adsorption of the inner Helmholtz plane

Rechargeable lithium metal batteries own the highest energy density among all electrochemical energy storage devices.Lithium metal anode in those cell system acts as paramount role in promoting high energy density[1].However,lithium anode tends to form dendrite morphology and exhibits huge volume expansion and high reactivity,which induces ultra-low columbic efficiency and out of tolerance cycle performance and even safety hazards[2,3].The lithium dendrite growth behavior is mainly decided by the high surface energy and diffusion barriers for Li ions in lithium batteries which is ascribed to thermodynamics factors and uneven electronic field distribution[1,4,5].During the repeated plating/stripping process,the structure and components of solid–liquid interphase are significantly determined by the deposition thermodynamics and kinetics.In the recent years,advances in characterization technology and the development of high-performance computing method have driven the rapid exploration of the fundamental theory of solid–liquid interphase in lithium batteries.

Enhancement of electrochemical performance in lithium-ion battery via tantalum oxide coated nickel-rich cathode materials

Nickel-rich cathode materials are increasingly being applied in commercial lithium-ion batteries to realize higher specific capacity as well as improved energy density.However,low structural stability and rapid capacity decay at high voltage and temperature hinder their rapid large-scale application.Herein,a wet chemical method followed by a post-annealing process is utilized to realize the surface coating of tantalum oxide on LiNi_(0.88)Mn_(0.03)Co_(0.09)O_(2),and the electrochemical performance is improved.The modified Li Ni_(0.88)Mn_(0.03)Co_(0.09)O_(2)displays an initial discharge capacity of~233 m Ah/g at0.1 C and 174 m Ah/g at 1 C after 150 cycles in the voltage range of 3.0 V–4.4 V at 45℃,and it also exhibits an enhanced rate capability with 118 m Ah/g at 5 C.The excellent performance is due to the introduction of tantalum oxide as a stable and functional layer to protect the surface of LiNi_(0.88)Mn_(0.03)Co_(0.09)O_(2),and the surface side reactions and cation mixing are suppressed at the same time without hampering the charge transfer kinetics.

Probing component contributions and internal polarization in silicon-graphite composite anode for lithium-ion batteries with an electrochemical-mechanical model

Silicon–graphite(Si–Gr)composite anodes are attractive alternatives to replace Gr anodes for lithium-ion batteries(LIBs)owing to their relatively high capacity and mild volume change.However,it is difficult to understand electrochemical interactions of Si and Gr in Si–Gr composite anodes and internal polarization of LIBs with regular experiment methods.Herein,we establish an electrochemical-mechanical coupled model to study the effect of rate and Si content on the electrochemical and stress behavior in a Si–Gr composite anode.The results show that the composites of Si and Gr not only improve the lithiation kinetics of Gr but also alleviate the voltage hysteresis of Si and decrease the risk of lithium plating in the negative electrode.What's more,the Si content is a tradeoff between electrode capacity and electrode volume variation.Further,various internal polarization contributions of cells using Si–Gr composite anodes are quantified by the voltage decomposition method.The results indicate that the electrochemical polarization of electrode materials and the electrolyte ohmic over-potential are dominant factors in the rate performance of cells,which provides theoretical guidance for improving the rate performance of LIBs using Si–Gr composite anodes.

Probing the improved stability for high nickel cathode via dual-element modification in lithium-ion

One of the major hurdles of nickel-rich cathode materials for lithium-ion batteries is the low cycling stability,especially at high temperature and high voltage,originating from severe structural degradation,which makes this class of cathode less practical.Herein,we compared the effect of single and dual ions on electrochemical performance of high nickel(LiNi_(0.88)Mn_(0.03)Co_(0.09)O_(2),NMC)cathode material in different temperatures and voltage ranges.The addition of a few amounts of tantalum(0.2 wt%)and boron(0.05 wt%)lead to improved electrochemical performance.The co-modified Li Ni_(0.88)Mn_(0.03)Co_(0.09)O_(2)displays an initial discharge capacity of 234.9 m Ah/g at 0.1 C and retained 208 m Ah/g at 1 C after 100 cycles at 45℃,which corresponds to a capacity retention of 88.5%,compared to the initial discharge capacity of234.1 m Ah/g and retained capacity of 200.5 m Ah/g(85.6%).The enhanced capacity retention is attributed to the synergetic effect of foreign elements by acting as a surface structural stabilizer without sacrificing specific capacity.

A high-performance rechargeable Li–O_2 battery with quasi-solid-state electrolyte

A novel transparent and soft quasi-solid-state electrolyte （QSSE） was proposed and fabricated, which consists of ionic liquid （PYR14TFSI） and nano-fumed silica. The QSSE demonstrates high ionic conductivity of 4.6× 10-4 S/cm at room temperature and wide electrochemical stability window of over 5 V. The Li-O2 battery using such quasi-solidstate electrolyte exhibits a low charge-discharge overpotential at the first cycle and excellent long-term cyclability over 500 cycles.

Enabling the thermal stability of solid electrolyte interphase in Li-ion battery

Lithium-ion batteries(LIBs)provide power for a variety of applications from the portable electronics to electric vehicles,and now they are supporting the smart grid.Safety of LIBs is of paramount importance in these scenarios.Specifically,thermal safety arouses increasing attention with the piling-up of LIBs.Heat generation can be significant.Hazardous incidents happen when thermal runaway occurs in a single cell level and drives the battery pack failure.Moreover,thermal runaway of LIBs is believed to originate from the exothermic reactions starting from the breakdown of the solid/cathode electrolyte interphase(SEI/CEI).To mitigate this challenge for a safe operation of LIBs,one straightforward and low-cost method is to build thermally stable SEI/CEI.This review gives an overview on the thermal behaviors of SEI/CEI as the first step in thermal runaway.We analyzed the electrolyte composition and the formation process of SEI/CEI that enable SEI/CEI of high thermal stability.It is identified that the stable lithium salts coupled with solvents of high boiling point is one way to enhance thermal stability of the battery system.In addition,the unsaturated bonds,halogen,phosphorus,sulfur,phenol,organic borate,borane,and silane are functional components to facilitate the formation of a thermally stable SEI/CEI,which is the immediate solution to boost thermal stability of high capacity electrodes.Moreover,in-situ polymerization/solidification is effective in enhancing simultaneously the electrochemical,chemical,and thermal stability.Finally,we revealed that only by constructing a stable SEI/CEI simultaneously could we harvest a battery system of high thermal stability.