An Active‐Oxygen‐Scavenging Oriented Cathode‐Electrolyte‐Interphase for Long‐Life Lithium‐Rich Cathode Materials

Abstract

energy density, low cost, and good thermal stability, which is a promising highperformance cathode material for lithiumion batteries. [2] Unlike ternary cathode materials, lithium cobalt oxide and other cathode materials, lithium-rich cathode materials (LR) can simultaneously invoke the redox of transition metal cations and oxygen anion. [3] The redox activity of oxygen in lithium-rich cathode materials provides innovative insights for high specific energy cathode materials, but it also brings a series of problems such as the change of crystal structure on the electrode surface, the release of oxygen and the decomposition of electrolyte. These severe problems often lead to continuous capacity fading and voltage decay on the cathode. [4] The electrochemical activation of Li 2 MnO 3 with superlattice component inevitably releases oxygen-active species, including oxygen (O 2 ), superoxide radicals (O 2• ¯), and singlet oxygen ( 1 O 2 ) during the first charge process. These oxygen-active species will decompose electrolyte solvents, accompanied by the generation of CO 2 , CO, and other gases. This reaction greatly destroys the structural stability of cathode materials and threatens the safety performance of batteries. [4b,5] Furthermore, unfavorable decomposition will be produced by carbonate electrolyte under severe conditions of high voltage, which is not conducive to the construction of a stable and robust cathode-electrolyte interface (CEI) layer and leads to the continuous consumption of active lithium ions. [6] Introducing electrolyte additives is one of the direct and effective methods to optimize the interface between cathode and electrolyte. A series of additives were developed to improve the cycling stability of lithium-ion batteries under high voltage, such as cathode film-forming additives (TPFPB, [7] TTFP, [8] FEC [9] ) flame-retardant additives (TFP, [10] TMP [11] ) and overcharge protection additives (BP, [12] 2,5-di-tert-butyl-1,4-dimethoxybenzene [13] ). In order to solve the problem of active oxygen in high-voltage LR mentioned above, superoxide radicals scavenger was proposed to eliminate oxygen free radicals that induced adverse reactions, thereby significantly improving the electrochemical stability of LR. [6b] In this work, β-carotene (C 40 H 56 ) was selected as a scavenging molecule, by adding it in electrolyte, to capture the active-oxygen Lithium-rich layered oxides with high energy density are promising cathode materials, thus having attracted a large number of researchers. However, the materials cannot be commercialized for application so far. The crucial problem is the releasing of lattice oxygen at high voltage and resulting consequence, such as decomposition of electrolyte, irreversible phase transition of crystal structure, capacity degradation, and voltage decay. Therefore, capturing active-oxygen and further constructing a cathode-electrolyte-interface (CEI) protective layer via the scavenging effects should be a fundamental step to solve these issues. Herein, β-carotene with...

Tuning of hybrid highly concentrated electrolytes and the interfacial building for lithium-based cells

“…Furthermore, the exothermic peaks of the HiF-related NCM811 and HiFA-6-related NCM811 were delayed to 250 °C and 255 °C, respectively, indicating that the CEI generated from the HCEs, especially HiFA-6, could contribute to the inhibition of lattice oxygen escape and was beneficial to enhancing the thermal stability of the NCM811 cathode. 42 Therefore, HiFA-6 showed great potential to improve the electrochemical performance, as well as the safety of high-voltage lithium metal batteries.…”

Regulating Lithium Plating/Stripping Behavior by a Composite Polymer Electrolyte Endowed with Designated Ion Channels

“…R S represents the impedance of the CPE and SPE, R SEI relates to the SEI and R ct belongs to the charge transport resistance, respectively. [ 41,42 ] R SEI and R ct from CPE are smaller than SPE, demonstrating that the SEI layer generated by Li/SPE/Li cell is thicker and Li + transport is hindered. The interfacial impedances of Li/CPE/Li cell at different current densities were also studied in Figure S11, Supporting Information.…”

Hollow Hemispherical Lithium Iron Silicate Synthesized by an Ascorbic Acid-Assisted Hydrothermal Method as a Cathode Material for Li Ion Batteries

“…The first charge curve showed a voltage plateau at 3.2 V, attributed to Fe 2+ /Fe 3+ oxidation [ 42 ]. When the voltage exceeded 4.2 V, another voltage plateau was formed due to the O 2− oxidation [ 43 ], which is similar to those caused by the oxidation of O 2− on Li-rich cathode materials [ 44 , 45 ] and Li 1.25 Nb 0.25 Fe 0.50 O 2 /C [ 46 ]. The first discharge curve became smooth at ~3.3 V, and then a plateau was formed, which is caused by the Fe 3+ /Fe 2+ reduction.…”