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 a cyclic carbonate, wherein the cyclic carbonate is a non-fluorinated cyclic carbonate;
15-30% by volume a non-cyclic carbonate;
40-70% by volume a linear ester;
a lithium salt in a concentration from 0.5 M to 1.5 M; and
lithium oxalate;
wherein the cyclic carbonate, the non-cyclic carbonate and the linear ester are present in a combined total volume of 100 vol % and the lithium oxalate is present at a concentration selected over the range of 0.05 M to 0.25 M.
2. The electrolyte of claim 1 , wherein the non-fluorinated cyclic carbonate is EC, the non-cyclic carbonate is selected from ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl propyl carbonate (MPC) or combinations thereof , the lithium salt includes LiPF 6 in a concentration from 0.8 to 1.20 M and the linear ester is selected from:
(i) methyl propionate;
(ii) ethyl propionate;
(iii) methyl butyrate;
(iv) ethyl butyrate;
(v) propyl butyrate;
(vi) butyl butyrate; or
(vii) a combination of (i), (ii), (iii), (iv), (v) and/or (vi).
3. The electrolyte of claim 2 , wherein at least two linear esters are present, a first linear ester selected from the group consisting of methyl propionate, ethyl propionate, methyl butyrate and ethyl butyrate and a second linear ester selected from the group consisting of propyl butyrate and butyl butyrate.
4. The electrolyte of claim 1 further comprising an additive selected from:
(i) lithium bis(oxalato)borate (LiBOB);
(ii) vinylene carbonate (VC); or
(iii) lithium difluoro(oxolato) borate (LiDFOB).
5. An electrochemical cell comprising:
an anode;
a cathode; and
the electrolyte of claim 1 provided between the anode and the cathode.
6. The electrochemical cell of claim 5 , 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 .
7. The electrochemical cell of claim 5 , 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.
8. The electrochemical cell of claim 5 wherein the anode is a carbon-based anode and the cathode is selected from a layered-layered composite of LiNiCoMnO 2 , LiNi 0.5 Mn 1.5 O 4 or LiNi 0.33 Co 0.33 Mn 0.33 O 2 .
9. 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.
10. A method of generating an electrical current, the method comprising the steps of:
providing an electrochemical cell according to claim 5 , the cell being in a charged state; and
discharging the electrochemical cell.