Electrolytes for wide operating temperature lithium-ion cells
Provided herein are electrolytes for lithium-ion electrochemical cells, electrochemical cells employing the electrolytes, methods of making the electrochemical cells and methods of using the electrochemical cells over a wide temperature range. Included are electrolyte compositions comprising a lithium salt, a cyclic carbonate, a non-cyclic carbonate, and a linear ester and optionally comprising one or more additives.
1. An electrolyte for use in an electrochemical cell, the electrolyte comprising a mixture of:
15-30% by volume cyclic carbonate, wherein the cyclic carbonate is a combination of mono-fluoroethylene carbonate (FEC) and EC wherein the FEC is present in an amount from 0.5 to 10% by volume;
15-30% by volume non-cyclic carbonate, wherein the non-cyclic carbonate is selected from ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl propyl carbonate (MPC) and combinations thereof;
40-70% by volume non-fluorinated linear ester, wherein the non-fluorinated linear ester is selected from: methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, and combinations thereof; and
a lithium salt in a concentration from 0.5 M to 1.5 M.
2. The electrolyte of claim 1 , wherein the non-cyclic carbonate is ethyl methyl carbonate (EMC), the lithium salt includes LiPF 6 in a concentration from 0.8 to 1.20 M and the non-fluorinated linear ester is selected from methyl propionate, methyl butyrate and combinations thereof.
3. The electrolyte of claim 1 , wherein at least two non-fluorinated linear esters are present, a first non-fluorinated linear ester having a low viscosity and selected from the group consisting of methyl propionate, ethyl propionate, methyl butyrate and ethyl butyrate and a second non-fluorinated linear ester having a high viscosity and selected from the group consisting of propyl butyrate and butyl butyrate.
4. The electrolyte of claim 1 further comprising an additive selected from lithium oxalate, lithium bis(oxalato)borate (LiBOB), vinylene carbonate (VC), lithium difluoro(oxolato) borate (LiDFOB) and combinations thereof.
5. The electrolyte of claim 1 further comprising an additive selected from lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxolato) borate (LiDFOB) and combinations thereof in a concentration of 0.05 to 0.25 M.
6. The electrolyte of claim 1 wherein the FEC is present in an amount from 2 to 10% by volume.
7. The electrolyte of claim 1 wherein the FEC is present in an amount from 0.5 to 5% by volume.
8. An electrochemical cell comprising:
an anode;
a cathode; and
the electrolyte of claim 1 provided between the anode and the cathode.
9. The electrochemical cell of claim 8 , wherein the cathode comprises a material selected from LiCoO 2 , LiMn 2 O 4 , LiMPO 4 (M=Fe, Co, Mn), LiNiCoAlO 2 , LiNi 0.33 CO 0.33 Mn 0.33 O 2 , LiNiCoO 2 , LiNi 0.8 Co 0.2 O 2 , Li(Li 0.17 Ni 0.25 Mn 0.58 )O 2 , layered-layered composite LiNiCoMnO 2 or LiNi 0.5 Mn 1.5 O 4 .
10. The electrochemical cell of claim 8 , wherein the anode comprises a material selected from natural graphite, synthetic graphite, hard carbon, mesocarbon microbeads (MCMB), silicon-carbon composites, lithium titanate (Li 4 Ti 5 O 12 ), lithium metal and combinations thereof.
11. The electrochemical cell of claim 8 wherein the anode is a carbon-based anode and the cathode is selected from LiFePO 4 , LiNiCoO 2 , LiNiCoAlO 2 , and a layered-layered composite of LiNiCoMnO 2 , LiNi 0.5 Mn 1.5 O 4 or Li Ni 0.33 Co 0.33 Mn 0.33 O 2 .
12. A method of making an electrochemical cell comprising the steps of:
providing a cathode;
providing an anode; and
providing the electrolyte of claim 1 between the cathode and the anode.
13. A method of generating an electrical current, the method comprising the steps of:
providing an electrochemical cell according to claim 8 , the cell being in a charged state; and
discharging the electrochemical cell.