Prevention of gassing in Si dominant lithium-ion batteries
A system and/or method for replacing solvents/additives such as fluoroethylene carbonate (FEC) to create new electrolyte compositions for lithium-ion energy storage devices with silicon-based electrode materials and reduce undesirable gassing. The electrolyte compositions may be used in an energy storage device comprising a first electrode and a second electrode, where at least one of the first electrode and the second electrode is a Si-based electrode, a separator between the first electrode and the second electrode, and the electrolyte composition.
1 . An energy storage device comprising a first electrode and a second electrode, wherein one or both of the first electrode and the second electrode is a Si-based electrode;
a separator between the first electrode and the second electrode; and
an electrolyte composition; wherein
said electrolyte composition comprises three or more solvents and one or more lithium salts;
wherein said solvents comprise one or more linear carbonates and two or more cyclic carbonates, where one of the cyclic carbonates is a fluorine-containing cyclic carbonate; and
wherein said electrolyte composition comprises 20-40% by weight of cyclic carbonates and about 50-80% by weight of linear carbonates;
wherein said two or more cyclic carbonates comprise fluoroethylene carbonate (FEC) and propylene carbonate (PC) where the ratio between FEC and PC is between 0.5 and 2;
wherein said one or more linear carbonates are selected from the group consisting of dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC); and
wherein the Si in said Si-based electrode is present as silicon particles having an average diameter between about 0.1 μm and about 30 μm; and
wherein said electrolyte composition comprises two lithium salts selected from the group consisting of LiTFSI, LIDFOB, LiFSi and LiPF 6 ;
wherein said electrolyte composition further comprises phosphazene in an amount of about 0.5-5% by weight; and
further comprising fluorobenzene (FB).
2 . The energy storage device of claim 1 , wherein the first electrode is a cathode comprising a layered lithium transition-metal oxide.
3 . The energy storage device of claim 2 , wherein the layered lithium transition-metal oxide comprises LiNi x Co y Mn z O 2 (NCM, 0≤x, y, z<1) or LiNi x Co y Al z O 2 (NCA, 0≤x, y, z<1).
4 . The energy storage device of claim 1 , wherein the second electrode is an anode comprising a Si-dominant electrode.
5 . The energy storage device of claim 4 , wherein the Si-dominant electrode contains greater than 50% silicon.
6 . The energy storage device of claim 1 , wherein said electrolyte composition is free of EC.
7 . The energy storage device of claim 1 , wherein said fluoroethylene carbonate (FEC) and propylene carbonate (PC) comprise more than 90% of the total cyclic carbonate content.
8 . The energy storage device of claim 1 , comprising LiFSi and LiPF 6 .
9 . The energy storage device of claim 8 , wherein the ratio between LiFSi and LiPF 6 is between 0.5 and 2.
10 . The energy storage device of claim 8 , further comprising LiDFOB in an amount of about 0.5-5% by weight.
11 . The energy storage device of claim 1 , wherein said fluorobenzene (FB) is present in an amount of about 5-20% by weight.