Electrolyte Regulating toward Stabilization of Cobalt-Free Ultrahigh-Nickel Layered Oxide Cathode in Lithium-Ion Batteries

Abstract

Cobalt (Co)-free ultrahigh-nickel (Ni) layered oxides exhibit dual competitive advantages in reducing the cathode cost and boosting the energy density, promising the sustainable development of batteries for electric vehicles. However, the increased Ni content and the resulting more highly oxidative Ni4+ potentially induce severe capacity fading due to the aggravated side reactions at the cathode surface, limiting the practical applications. Here, we evaluate the compatibility of two localized high-concentration electrolytes (LHCEs) with LiNi0.96Mg0.02Ti0.02O2 (NMT) cathode under a high charging voltage of 4.4 V in lithium-ion batteries. The LHCE with ethylene carbonate as additive enables the formation of effective interfacial layers on both the NMT cathode and graphite anode, realizing a capacity retention of 97.2% after 200 cycles and high reversible capacities of ∼180.2 and ∼185.8 mAh g–1 at 5C charge rate and 5C discharge rate, respectively, at 25 °C. This work provides a promising approach to enable Co-free ultrahigh-Ni layered oxides for practical applications.

Ethylene Carbonate‐Free Electrolytes for Stable, Safer High‐Nickel Lithium‐Ion Batteries

“…[6,10] This process not only leads to the generation of protons that can further induce a decomposition of lithium hexafluorophosphate (LiPF 6 ) to form hydrofluoric acid (HF), [11][12][13] but also causes the formation of spinel-like and rock salt-like phases at the cathode/electrolyte interphase (CEI). [14][15][16][17][18] Moreover, the generated TM ions and HF can crossover and exert side effects on the performance of Gr anodes. [19][20][21] In addition, EC molecules can also easily react with the oxygen released from high-Ni cathodes at elevated temperatures, leading to a catastrophic heat release and eventual safety hazards.…”

Toward the Practical Use of Cobalt-Free Lithium-Ion Batteries by an Advanced Ether-Based Electrolyte

“…To the best of our knowledge, it is the highest capacity retention achieved in Co-free highenergy LIBs operated under similar or even milder conditions. 4,5,9 Such capacity retention is even superior to some Co-containing cell chemistry such as Gr||NMC811. 6 To verify the effectiveness of the E-DME-F electrolyte in the Gr||NMT cells under relatively practical situations, SLPCs and high capacity loading DLPCs were assembled and evaluated.…”

“…The precursor of the LiNi 0.96 Mg 0.02 Ti 0.02 O 2 (NMT) cathode was synthesized via a coprecipitation method following the procedure in our previous publication. 5 A stoichiometric mixture (Ni/Mg/Ti = 96:2:2 by mol.) of NiSO 4 •6H 2 O (98%, Fisher Chemical), MgSO 4 •7H 2 O (≥98%, Sigma-Aldrich), and TiOSO 4 (15 wt % in dilute sulfuric acid, 99.99% trace metals basis, Sigma-Aldrich) was mixed with concentrated sulfuric acid (95−98%, Sigma-Aldrich).…”

“…Therefore, it is indispensable to modify LNO to improve the life span of the LNO-based LIBs. LiNi 0.96 Mg 0.02 Ti 0.02 O 2 (NMT) material, derived from LNO by doping magnesium (Mg) and titanium (Ti), emerged as a promising candidate for building Co-free cells as it exhibits high specific capacity and energy density as well as good capacity retention in graphite (Gr)||NMT cells. , Despite its success, the cycle life of the Gr||NMT is still limited. According to the report by Mu et al, the capacity retention of Gr||NMT with the conventional LiPF 6 -organocarbonate electrolyte was 77% in a coin cell setup after 300 charge/discharge cycles, which is not fully adequate for practical uses.…”

Dual‐Salt Electrolyte with Synergistic Effect for Lithium Metal Batteries with Prolonging Cyclic Performance

“…Therefore, to achieve a high-energy-density Li metal battery with the high-voltage NCM811 cathode, we suggest that interface regulation based on carbonate electrolyte is the promising approach to prolong the cyclic life of Li metal batteries. [32] Under the consideration of the applied condition of highvoltage, the all-carbonate solvent was selected. ethylene carbonate (EC) embraces the higher dielectric constant, which can enhance the solubility of Li salt in carbonate solvents.…”