Synergetic effect of aqueous electrolyte and ultra‐thick millimeter‐scale LiFePO ₄ cathode in aqueous lithium‐ion batteries

Abstract

Aqueous rechargeable lithium-ion batteries (ARLBs) have garnered substantial attention for their desirable properties of safety, environmental compatibility, and rapid ion-transport in the electrolyte compared with organic lithium-ion batteries. However, the low energy density of ARLBs and poor electrochemical stability of the aqueous electrolyte are critical limitations. A proposed means of improving the energy density of ARLBs is the fabrication of thick electrodes, wherein the fraction of active material is increased and that of inactive material decreased without modifying the structure of the electrode. This study describes the construction of ultra-thick millimeter-scale LiFePO 4 (LFP) electrodes containing Li 2 SO 4 at various concentrations to control the conductivity of the aqueous electrolyte. The enhanced electrolyte conductivity mitigates sluggish electrochemical behavior by providing high lithium-ion flux even in 2.0 mm-thick LFP electrodes having a capacity of 52 mAh cm À2 . A straightforward method of electrode preparation is described. The operation of mm-thick LFP electrodes evaluated with a homemade three-electrode cell shows improved cycle performance and rate capability that are not attainable with organic electrolytes.

Effect of Electrolyte Concentration on the Electrochemical Performance of Spray Deposited LiFePO4

“…In order to find the appropriate electrolyte concentration, the cyclic voltammetry (CV) curves were evaluated in 0.5 M, 1 M, and 2 M LiOH electrolytes ( Figure 4 a–c). The curves exhibit an almost rectangular shape, with two inconspicuous peaks in the redox processes (i.e., at approximately −0.5 V (cathode) and +0.3 V (anode)) indicating a non-faradaic charging process [ 47 ]. This process is based on the formation of a double layer at the electrode–electrolyte interface during the adsorption of Li + on LiFePO 4 film surface, as proposed in Equation (1) [ 47 , 48 , 49 ].…”

“…The curves exhibit an almost rectangular shape, with two inconspicuous peaks in the redox processes (i.e., at approximately −0.5 V (cathode) and +0.3 V (anode)) indicating a non-faradaic charging process [47]. This process is based on the formation of a double layer at the electrode-electrolyte interface during the adsorption of Li + on LiFePO 4 film surface, as proposed in Equation ( 1) [47][48][49]. In that case, the charge is mainly stored in the electrolyte and the electrolyte concentration is therefore expected to affect the cathode's performance [50].…”

Review—Flow Batteries from 1879 to 2022 and Beyond

“…50-100 mAh cm −2 ). 329,[331][332][333][334][335][336][337][338][339] Due to finite ionic and electronic conductivities of the layers, thick layers would be underutilized during charge-discharge cycles. 340 For this reason, SEAM batteries are not cost-effective in applications with multi-hour half-cycle duration.…”

Booster Adhesion of Crystalline Poly(vinylidene fluoride) Binder by Heat Treatment for Ni‐rich Layered Oxide Cathode in Lithium‐ion Batteries

“…Polymers such as PVDF, styrene butadiene rubber (SBR), and polytetrafluoroethylene (PTFE), are commonly used as binders in battery electrodes. [11,[13][14][15][16][17] An electrochemically and oxidatively stable polymer is required for the positive electrode. Additionally, the Li ions of of the cathode active materials can be dissolved in the aqueous binder solutions.…”

“…In battery electrode manufacturing process, a slurry type mixture is cast onto the current collector foil, and the electrode matrix held together by an adhesive binder. Polymers such as PVDF, styrene butadiene rubber (SBR), and polytetrafluoroethylene (PTFE), are commonly used as binders in battery electrodes [11,13–17] . An electrochemically and oxidatively stable polymer is required for the positive electrode.…”