Lithium-silica nanosalt as a low-temperature electrolyte additive for lithium-ion batteries

• A lithium-modified silica nanosalt (Li–SiO2, coded Li202) of hydrophobic fumed silica (R202) is synthesized.
• The obtained Li202 nanosalt (2.5 wt%) is added into an electrolyte solution of 1.0 M LiPF6 dissolved in organic electrolyte.
• The electrolyte solution including the Li202 nanosalt shows high conductivity and superior electrochemical stability over 5 V.
• The high-rate capability at −20 °C of the LiCoO2/graphite cell is particularly enhanced by adding Li202 nanosalt.

A lithium-modified silica nanosalt (Li–SiO2, coded Li202) of hydrophobic fumed silica (R202) is synthesized to use as an electrolyte additive for lithium-ion batteries (LIBs) under low temperature conditions. The synthesis method consists of reacting the silica nanoparticles with LiH and consequently quickly reacting the conjugate silicate ions with 1,3-propanesultone as a surface stabilizer. The obtained Li202 nanosalt (2.5 wt%) is added into an electrolyte solution of 1.0 M LiPF6 dissolved in ethylene carbonate/propylene carbonate/ethylmethyl carbonate/diethyl carbonate (20:5:55:20 vol%) + 2 wt% vinylene carbonate. The electrolyte solution including the Li202 nanosalt shows higher ionic conductivity and superior electrochemical stability over 5 V, which is due to the stabilized surface group. The high-rate capability at −20 °C of the LiCoO2/graphite cell is particularly enhanced by adding Li202 nanosalt. In addition, excellent cycle performance at −20 °C endorses the use of Li202 nanosalt as a low-temperature electrolyte additive for LIBs.