Interface engineering strategy via electron-defect trimethyl borate additive toward 4.7 V ultrahigh-nickel LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)battery

The Li metal battery with ultrahigh-nickel cathode(LiNi_(x)M_(1-x)O_(2),M=Mn,Co,and x≥0.9)under high-voltage is regarded as one of the most promising approaches to fulfill the ambitious target of 400 Wh/kg.However,the practical application is impeded by the instability of electrode/electrolyte interface and Ni-rich cathode itself.Herein we proposed an electron-defect electrolyte additive trimethyl borate(TMB)which is paired with the commercial carbonate electrolyte to construct highly conductive fluorine-and boron-rich cathode electrolyte interface(CEI)on LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)(NCM90)surface and solid electrolyte interphase(SEI)on lithium metal surface.The modified CEI effectively mitigates the structural transformation from layered to disordered rock-salt phase,and consequently alleviate the dissolution of transition metal ions(TMs)and its“cross-talk”effect,while the enhanced SEI enables stable lithium plating/striping and thus demonstrated good compatibility between electrolyte and lithium metal anode.As a result,the common electrolyte with 1 wt%TMB enables 4.7 V NCM90/Li cell cycle stably over 100 cycles with 70%capacity retention.This work highlights the significance of the electron-defect boron compounds for designing desirable interfacial chemistries to achieve high performance NCM90/Li battery under high voltage operation.

A weakly-solvated ether-based electrolyte for fast-charging graphite anode

Weakly-solvated electrolytes(WSEs)utilizing solvents with weak coordination ability offer advantages for low-potential graphite anode owing to their facile desolvation process and anions-derived inorganic-rich solid electrolyte interphase(SEI)film.However,these electrolytes face challenges in achieving a balance between the weak solvation affinity and high ionic conductivity,as well as between rigid inorganic-rich SEI and flexible SEI for long-term stability.Herein,we introduce 1,3-dioxolane(DOL)and lithium bis(trifluoromethanesulfonyl)-imide(LiTFSI)as functional additives into a WSE based on nonpolar cyclic ether(1,4-dioxane).The well-formulated WSE not only preserves the weakly solvated features and anion-dominated solvation sheath,but also utilizes DOL to contribute organic species for stabilizing the SEI layer.Benefitting from these merits,the optimized electrolyte enables graphite anode with excellent fast-charging performance(210 mAh/g at 5 C)and outstanding cycling stability(600 cycles with a capacity retention of 82.0%at room temperature and 400 cycles with a capacity retention of 80.4%at high temper-ature).Furthermore,the fabricated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)||graphite full cells demonstrate stable operation for 140 cycles with high capacity retention of 80.3%.This work highlights the potential of tailoring solvation sheath and interphase properties in WSEs for advanced electrolyte design in graphite-based lithium-ion batteries.