In Situ Li₃PO₄/PVA Solid Polymer Electrolyte Protective Layer Stabilizes the Lithium Metal Anode

Abstract

A lithium metal anode is regarded as the most promising anode material for the next generation of high-energy density batteries because of its high specific capacity and low reduction potential. However, dendritic deposition and severe side reactions in continuous Li plating/stripping inevitably hinder the practical application of Li metal batteries. A solid polymer electrolyte protective layer with synergistic Li3PO4/polyvinyl alcohol (PVA) features is in situ constructed on a lithium metal anode to obtain a stable interface during charge/discharge cycles. The protective layer can adapt to volume changes and inhibit lithium dendrites. The in situ reaction guaranteed the uniformity of ion transport and a tight interface between the protective layer and the lithium metal, so that the lithium deposition behavior was effectively regulated. The PP-Li anode presented a stable Li plating/stripping for 1000 h in a symmetrical cell system and exhibited an enhanced performance of the lithium titanium oxide cell. The in situ Li3PO4/PVA solid polymer electrolyte protective layer provided a promising strategy to tackle the challenges raised by the intrinsic properties of the lithium metal anode.

Role of Critical Oxygen Concentration in the β-Li3PS4–xOx Solid Electrolyte

“…Further, SEI is likely to be disordered, containing defects as well. As such, we do not expect that the conductivity of Li 3 PO 4 will be a limiting factor at the SEI, as demonstrated in earlier experimental studies. , …”

“…Similarly, the chemical reactivity of Li 3 PS 3.75 O 0.25 with the Li metal anode and LiCoO 2 cathode follows the same principle and is therefore similar to that of Li 3 PS 4 (Figure b and Tables S5 and S6). However, the interfacial reaction product composition for Li 3 PS 3.75 O 0.25 differs from Li 3 PS 4 due to the formation of Li 3 PO 4 at the Li-metal/Li 3 PS 3.75 O 0.25 interfaces in fractional quantities, which can potentially stabilize the interface at higher voltages. , Notably, the amount of Li 3 PO 4 at the solid electrolyte interphase (SEI) is small due to the limited amount of O in Li 3 PS 3.75 O 0.25 . Further, SEI is likely to be disordered, containing defects as well.…”

“…As such, we do not expect that the conductivity of Li 3 PO 4 will be a limiting factor at the SEI, as demonstrated in earlier experimental studies. 55,56 AIMD simulations with NVT ensemble were carried out at 600−1300 K with a 100 K interval, for Li 3 PS 4−x O x ; x = 0, 0.125, 0.25, 0.50, and 1.0. Higher levels of oxygenation beyond x = 1 were not further explored given that such structures are not expected to be stable (Figure 1b).…”

Additive stabilization of SEI on graphite observed using cryo-electron microscopy

“…We see large quantities of Li 3 PO 4 formed in the SEI. These [10][11][12] The Li metal is slightly more electronegative than graphite, therefore such in-situ formed Li 3 PO 4 layer on graphite anode should be even more stable, enhancing the stability and life of batteries. The schematic in Figure 3g illustrates the SEI architecture formed with DTD or TPP additive, where a dense layer of polycrystalline inorganic nanocrystals dominates the SEI functions, and the grain boundaries may also play important roles in Li + transport across the SEI.…”

In Situ Synthesis of a Li6.4La3Zr1.4Ta0.6O12/Poly(vinylene carbonate) Hybrid Solid-State Electrolyte with Enhanced Ionic Conductivity and Stability

“…However, their intrinsic grid structure leads to the brittle character and poor contact with electrodes, which limit their practical applications. Polymer SSEs, such as polyethylene oxide (PEO), − polyvinyl alcohol (PVA), , polyacrylonitrile (PAN), , and poly­(methyl methacrylate) (PMMA), , can transport Li + through the segmental motion of polymers, which are flexible, easily manufactured, and demonstrate improved compatibility with the electrodes. However, their applications are quite limited because of the poor ionic conductivity, especially at ambient temperature .…”