To further increase the energy density of lithium-ion batteries (LIBs), various researches have been conducted on high-voltage and high-capacity cathode materials. In this perspective, monoclinic Li₃V₂(PO₄)₃ is a promising candidate due to its promising theoretical discharge capacity of 197 mAh/g with complex phase transition in the voltage range of 3.0 to 4.8 V. However, such asymmetric phase transition behavior with 3 Li⁺ ion extraction/insertion is highly irreversible, resulting in an initial discharge capacity of 163 mAh/g with deteriorated capacity retention. We suggest that cycling Li₃V₂(PO₄)₃ in the voltage range of 3.0 to 4.5 V suppresses the irreversible phase transition and elution of transition metal. Hence, Li₃V₂(PO₄)₃ in the voltage range of 3.0 to 4.5 V delivers an initial discharge capacity of about 142 mAh/g and exhibits extremely long cycle retention (78.70% 2,000 cycles), as when cycling in the voltage range of 3.0 to 4.3 V (81.67% 2,000 cycles). Furthermore, we present the possibility of a Li₃V₂(PO₄)₃||Li₃V₂(PO₄)₃ symmetric all-solid-state battery based on an N/P ratio and a cutoff voltage design, which is demonstrated in liquid electrolyte half-cells and symmetric full cells.

We have entered the age of renewable energy revolution. Hence, energy-dense all-solid-state lithium metal batteries are now being actively researched as one of the most promising energy storage systems. However, they have not yet been a silver bullet due to the dendrite formation and interfacial issue. Here, we introduce the hybrid polymer electrolyte via a novel solvent-free strategy as well as utilize a polymerization and gelation effect of cyanoethyl polyvinyl alcohol to achieve superior electrochemical performance. The hybrid polymer electrolyte, using cyanoethyl polyvinyl alcohol, demonstrates a stable artificial solid electrolyte interface layer, which suppresses the continuous decomposition of Li salts. Importantly, we also present the lithium-graphite composite anode to reach the super-high-energy-density anode materials. Taken together, these advancements represent a significant stride toward addressing the challenges associated with all-solid-state lithium metal batteries.

Arising from the increasing demand for electric vehicles (EVs), Ni-rich LiNi_xCo_yMn_zO₂ (NCM, x + y + z = 1, x ≥ 0.8) cathode with greatly increased energy density are being researched and commercialized for lithium-ion batteries (LIBs). However, parasitic crack formation during the discharge–charge cycling process remains as a major degradation mechanism. Cracking leads to increase in the specific surface area, loss of electrical contact between the primary particles, and facilitates liquid electrolyte infiltration into the cathode active material, accelerating capacity fading and decrease in lifetime. In contrast, Ni-rich NCM when used as a single crystal exhibits superior cycling performances due to its rigid mechanical property that resists cracking during long charge–discharge process even under harsh conditions. In this paper, we present comparative investigation between single crystal Ni-rich LiNi_0.92Co_0.04Mn_0.04O₂ (SC) and polycrystalline Ni-rich LiNi_0.92Co_0.04Mn_0.04O₂ (PC). The relatively improved cycling performances of SC are attributed to smaller anisotropic volume change, higher reversibility of phase transition, and resistance to crack formation. The superior properties of SC are demonstrated by in situ characterization and battery tests. Consequently, it is inferred from the results obtained that optimization of preparation conditions can be regarded as a key approach to obtain well crystallized and superior electrochemical performances.

The electrical characteristics of hybrid super capacitor were evaluated by synthesizing LTO (Li₄Ti₅O₁₂) using TiO₂ having a hydrogen titanate nanowire form. Preparation of the hydrogen titanate nanowire was implemented by using TiO₂ having size of 60 nm and NaOH, and performing synthesis at 70 ℃ for 6 h with a sonochemical method. LTO compound was synthesized at 150 ℃ for 36 h and at 180 ℃ for 36 h respectively by using the hydrogen titanate nanowire and LiOH·H₂O as starting materials with a hydrothermal method. The final LTO compound was synthesized at 700 ℃ for 6 h using a solid-state method. As a result of manufacturing the hybrid super capacitor using LTO synthesized at 180 ℃ for 36 h with the hydrothermal method, a capacity of 198 mA·h/g has been achieved compared to a theoretical capacity of 172 mA·h/g of existing LTO, and thus, the capacity has been increased by about 13%. Further, such excellent cycle performance has ensured its possibility as a high-capacity capacitor.