Electrolytes for stable cycling of high capacity lithium based batteries
Electrolytes are described with additives that provide good shelf life with improved cycling stability properties. The electrolytes can provide appropriate high voltage stability for high capacity positive electrode active materials. The core electrolyte generally can comprise from about 1.1M to about 2.5M lithium electrolyte salt and a solvent that consists essentially of fluoroethylene carbonate and/or ethylene carbonate, dimethyl carbonate and optionally no more than about 40 volume percent methyl ethyl carbonate, and wherein the lithium electrolyte salt is selected from the group consisting of LiPF 6 , LiBF 4 and combinations thereof. Desirable stabilizing additives include, for example, dimethyl methylphosphonate, thiophene or thiophene derivatives, and/or LiF with an anion complexing agent.
1. A lithium ion battery comprising a positive electrode, a negative electrode, and a separator separating the positive electrode and the negative electrode, wherein the positive electrode comprises an active material comprising a lithium rich metal oxide, and an electrolyte, wherein the electrolyte comprises:
solvent, from about 1.1M to about 2.5M lithium electrolyte salt, from about 0.01 to about 0.4 wt % dimethyl methylphosphonate and an optional lithium salt additive, wherein the solvent comprises fluoroethylene carbonate and/or ethylene carbonate, and a liquid organic solvent selected from the group consisting of dimethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, γ-valerolactone or a combination thereof and wherein the lithium electrolyte salt is selected from the group consisting of LiPF 6 , LiBF 4 and combinations thereof,
wherein the positive electrode active material has a specific capacity of at least about 140 mAh/g at a 1C rate discharged from 4.35V to 2V and wherein the battery has a capacity at the 500th cycle that is at least about 94% of the 5th cycle capacity when cycled at a discharge rate of 1C from 4.35V to 2.5V.
2. The lithium ion battery of claim 1 wherein the electrolyte comprises from about 1.15M to about 1.6M lithium electrolyte salt.
3. The lithium ion battery of claim 1 wherein the electrolyte comprises from about 0.05 to about 0.2 wt % dimethyl methylphosphonate.
4. The lithium ion battery of claim 1 further comprising from about 0.1 wt % to about 5 wt % LiBOB, LiDFOB or a combination thereof.
5. The lithium ion battery of claim 1 wherein the solvent consists essentially of ethylene carbonate and dimethyl carbonate at a weight ratio from about 1:1 to about 1:4 and methylethyl carbonate at a concentration relative to the total electrolyte weight from 0 to about 30 weight percent.
6. The lithium ion battery of claim 5 wherein the weight ratio of ethylene carbonate to dimethyl carbonate is from about 1:1.25 to about 1:3 and the electrolyte comprises from about 5 weight percent to about 20 weight percent methylethyl carbonate.
7. The lithium ion battery of claim 1 wherein the solvent consists essentially of fluoroethylene carbonate and dimethyl carbonate at a weight ratio from about 1:1 to about 1:4.
8. The lithium ion battery of claim 1 wherein the negative electrode comprises graphitic carbon, the lithium rich metal oxide is approximately represented by the formula Li 1+b Ni α Mn β Co γ A δ O 2−z F z , where b ranges from about 0.01 to about 0.3, α ranges from about 0 to about 0.4, β ranges from about 0.2 to about 0.65, γ ranges from 0 to about 0.46, δ ranges from 0 to about 0.15 and z ranges from 0 to about 0.2 with the proviso that both α and γ are not zero, and where A is a metal element different from Ni, Mn, Co, or a combination thereof, and the battery exhibit manganese dissolution of no more than about 140 parts per million by weight (ppm) within the negative electrode removed from the battery following a first charge 4.35V at constant current of, C/10, a discharge to 2.0V at C/10, a second charge to 4.35V at C/10, storage after the second charge for a week at 60° C. at 100% state of charge and discharged prior to disassembly the analyze the negative electrode.
9. The lithium ion battery of claim 2 wherein the weight ratio of ethylene carbonate to dimethyl carbonate is from about 1:1.25 to about 1:3 and the electrolyte comprises from about 5 weight percent to about 20 weight percent methyl ethyl carbonate.
10. The lithium ion battery of claim 9 further comprising from about 0.1 wt % to about 5 wt % LiBOB, LiDFOB or a combination thereof.
11. The lithium ion battery of claim 7 wherein the electrolyte comprises from about 1.15M to about 1.6M lithium electrolyte salt.
12. The lithium ion battery of claim 7 wherein the electrolyte further comprises from about 0.1 wt % to about 5 wt % LiBOB, LiDFOB or a combination thereof.
13. The lithium ion battery of claim 1 wherein the electrolyte further comprises from about 0.1 wt % to about 5 wt % LiBOB, LiDFOB or a combination thereof.
14. The lithium ion battery of claim 1 wherein the electrolyte comprises from about 1.15M to about 1.6M lithium electrolyte salt, wherein the weight ratio of ethylene carbonate to dimethyl carbonate is from about 1:1.25 to about 1:3.
15. The lithium ion battery of claim 1 wherein the positive electrode active material comprises an inorganic stabilization coating comprising metal oxide, metal halide or a combination thereof with an average thickness from about 0.5 nm to about 12 nm.
16. The lithium ion battery of claim 1 wherein the negative electrode comprises graphitic carbon.
17. The lithium ion battery of claim 1 wherein the negative electrode comprises a silicon based active material.
18. The lithium ion battery of claim 1 wherein the battery has a capacity at the 500th cycle that is at least about 97.5% of the 5th cycle capacity when cycled at a discharge rate of 1C from 4.35V to 2.5V.