Boosting the Temperature Adaptability of Lithium Metal Batteries via a Moisture/Acid‐Purified, Ion‐Diffusion Accelerated Separator

Abstract

solutions, explorative studies of the electro-redox couples, with the concurrent high retrievable capacity, enlarged nominal voltage gap, and rapid reaction kinetics, hold the key to promote the energy-dense battery construction at the extreme power output. [1] For the lithium ion batteries, the energy densities of traditional formats (LiCoO 2 /LiFePO 4 cathodes and graphite anodes) have approached their theoretical limits. [2] Alternatively, the unit cell prototyping of the high-capacity Li metal anode with the nickel-rich cathode can achieve the enhanced level of energy densities at the device level. [3,4] When soaking this electrode couples in the conventional carbonate-based electrolytes, however, the Fermi-energy incompatibility at the multiscale interface would cause the uncontrollable dendrite growth on the metallic foil and cathode structure collapse upon the high-voltage cycling. [5] Therefore, the reliable operation of the energy-dense battery necessitates the harmony balance of the enlarged voltage gap and the interfacial stability at multiple scales, yet still remains challenging.As the most attractive cathode type of the practical relevance, nickel-rich (Ni content >0.8) layered oxides exhibit the merits of the large specific capacity (>200 mAh g −1 ), environmental benignity and relative lower cost as compared to the LiCoO 2 cathode. Despite of the dominant nickel occupancy in the layered oxides for elevating the Li storage sites, the increased nickel ratio adversely deteriorates the cycle performance. The transition metal (TM) layer of the oxide structure at the highvoltage charged states would oxidize the carbonate solvents in the presence of moisture, leading to serious self-discharge rates upon the high-temperature storage. [6] Additionally, the hydrofluoric acid (HF) formed by the decomposition of the lithium hexafluorophosphate (LiPF 6 ) salt aggravates the TM ions (Co 2+ , Ni 2+ , and Mn 2+ ) dissolution and structural collapse of the layered cathode, meanwhile the TM species would deposit on the anode surface and degrade the solid electrolyte interface (SEI). [7] So far, a plethora of mitigation strategies were implemented to insulate the direct contact of the oxide particles with the electrolyte, for instance the exquisite coatings with The reliable operation of Li metal batteries suffers from cathode collapse due to high-voltage cycling, interfacial reactivity of the Li deposits, self-discharge at the elevated temperatures, as well as the power output deterioration in low-temperature scenarios. In contrast to the individual electrode optimization, herein, a hetero-layered separator with an asymmetric functional coating on polyethylene is proposed in response to the aforementioned issues: On the face-to-cathode side, the hybrid layer of the molecular sieve and sulfonated melamine formaldehyde can scavenge the hydrofluoric acid and moisture residues from the carbonate electrolyte, maintaining the cathode robustness in both the high-voltage cycling or high-temperature storage scenarios; while...

Enabling 420 Wh kg −1 Stable Lithium‐Metal Pouch Cells by Lanthanum Doping

“…Such performance is outstanding compared with other celllevel pouch cells reported from literature. [51][52][53] As demonstrated above, the La-doped Li metal validates remarkable properties of both coin cell and pouch cell, showing a tremendous potential toward the practical realization of stable Li-metal batteries.…”

“…At the same time, the E/C ratio is limited to a very lean level of 1.76 g Ah −1 , which is remarkably lower than the values in previous reports in the literature. [50,51] The specific energy of the assembled pouch cell is based on the total weight of all parts, including the cathode, anode, electrolyte, separator, and package (see cell parameters in Table S5, Supporting Information). As expected, the cycle stability of the high-energy Li-metal pouch cell is brilliant.…”

Direct Fabrication of PET-Based Thermotolerant Separators for Lithium-Ion Batteries with Ion Irradiation Technology

“…Before measurement, the electrolyte-soaked separator was assembled into a Li/separator/Li coin cell and rested for 12 h. Then, the obtained coin-type cell was used to perform the polarization test at a constant potential of 10 mV for 1000 s. Meanwhile, the AC impedance test was carried out before and after polarization with the frequency in the range of 1–10 6 Hz. The t Li + was calculated according to the Bruce–Vincent–Evans equation (eq ) ,, t normalL i + = I normals normals ( Δ V − I 0 R 0 ) I 0 ( Δ V − I s s R s s ) where I ss and I 0 are the steady-state current and initial current deduced from the chronoamperometry, respectively. The applied polarization voltage is denoted as Δ V (10 mV).…”

A separator rich in SnF2and NO3−directs an ultra-stable interface toward high performance Li metal batteries

“…Based on this principle, many materials including inorganic species, organic molecules and polymers are employed as functional layers for modifying the traditional polypropylene (PP) separator. [44][45][46][47][48][49][50][51][52][53] Although these coating materials can act to suppress Li dendrites and form SEI for protecting the Li anode, inorganic coatings cause a decrease in porosity to an increased impedance, while organic molecules and polymers carry the defect of poor thermal stability. 54 Therefore, designing a functional separator for LMBs that stands up to practical conditions such as high voltage, high current, low N/P ratio, lean electrolyte content and extreme temperatures remains a demanding goal.…”