A secondary battery includes: a cathode; an anode; and an electrolyte, wherein the cathode includes a cathode current collector; a carbon layer including a binder, and carbon; and an active material layer, and the electrolyte includes lithium hexafluorophosphate (LiPF.sub.6) and lithium bis (fluorosulfonyl)imide (LiFSI). The secondary battery according to the present invention may have improved high-temperature and low-temperature properties, and may inhibit corrosion of a cathode to have increased life.

An electrolyte including a dinitrile compound, a trinitrile compound, and propyl propionate. Based on the total weight of the electrolyte, the weight percentage of the dinitrile compound is X, the weight percentage of the trinitrile compound is Y, and the weight percentage of the propyl propionate is Z, wherein, about 2.2 wt %≤(X+Y)≤about 8 wt %, about 0.1≤(X/Y)≤about 2.3, about 5 wt %≤Z≤about 50 wt %, 1 wt %<Y<5 wt %, and about 0.02≤(Y/Z)≤about 0.3; wherein wherein the dinitrile compound is one or more compounds selected from the group consisting of butanedinitrile, adiponitrile, and 1,4-dicyano-2-butene; and the trinitrile compound is one or more compounds selected from the group consisting of 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile and 1,2,3-tris(2-cyanoethoxy)propane.

The present application provides a lithium ion battery, comprising an electrode assembly and an electrolyte comprising a fluorosulfonate and/or difluorophosphate substance. The lithium ion battery has a gas generation area coefficient during formation, defined as α, with α=M×S/200; wherein M is in the range of 5 mg/cm.sup.2-100 mg/cm.sup.2; S is the specific surface area of the negative electrode material on the negative electrode current collector and is in the range of 0.1 m.sup.2/g-10 m.sup.2/g; the lithium ion battery has a gas venting path coefficient defined as β, with β=100/L, wherein L is in the range of L≥50 mm; the mass percentage content w % of the fluorosulfonate and/or difluorophosphate substance in the electrolyte and α and β meet the equation 0.01≤w×β/α≤20.

Disclosed herein are electrolyte compositions comprising: a) a first solvent comprising a cyclic carbonate; b) a second solvent comprising a non-fluorinated acyclic carbonate; c) at least one electrolyte component selected from: i) a fluorinated acyclic carboxylic acid ester; ii) a fluorinated acyclic carbonate; iii) a fluorinated acyclic ether; or iv) a mixture thereof; and d) an electrolyte salt; wherein the electrolyte component is present in the electrolyte composition in the range of from about 0.05 weight percent to about 10 weight percent, based on the total weight of the first and second solvents.

The present disclosure relates to prelithiated Si electrodes, methods of prelithiating Si electrodes, and use of prelithiated electrodes in electrochemical devices are described. There are several characteristics of electrode prelithiation that enable the superior battery performance. First, a prelithiated silicon anode is already in its expanded state during SEI formation, and therefore less of the SEI layer breaks down and reforms during cycling. Second, the prelithiated anode has a lower anode potential, which may also help the cycle performance of an electrochemical device.

A lithium battery including: a cathode; an anode; and an electrolyte between the cathode and the anode, wherein the electrolyte includes a lithium salt and a non-aqueous solvent including ethylene carbonate (EC), an amount of the EC per 100 parts by volume of the non-aqueous solvent is about 5 parts by volume to about 15 parts by volume, and wherein the cathode includes a cathode active material represented by Formula 1,
Li.sub.xNi.sub.yM.sub.1-yO.sub.2-zA.sub.z  Formula 1 wherein, in Formula 1, 0.9≤x≤1.2, 0.7≤y≤0.98, and 0≤z≤0.2, M is Al, Mg, Mn, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Bi, or a combination thereof, and A is an element having an oxidation number of −1 or −2,
wherein each element of M is independently present in an amount of 0<(1−y)≤0.3,
wherein an total content of M is 0.02≤(1−y)≤0.3.

Localized superconcentrated electrolytes (LSEs) and electrochemical devices including the LSEs are disclosed. The LSE includes an active salt, a solvent in which the active salt is soluble, and a diluent in which the active salt is insoluble or poorly soluble, wherein the diluent includes a fluorinated orthoformate.

An electrochemical cell according to various aspects of the present disclosure includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive electroactive material. The positive electroactive material includes a phospho-olivine compound. The negative electrode includes lithium metal. The separator is between the positive electrode and the negative electrode. The separator is electrically insulating and ionically conductive. The electrolyte includes a ternary salt and a solvent. The ternary salt includes LiPF.sub.6, LiFSI, and LiClO.sub.4.

An electrolyte for a lithium ion battery includes a nonaqueous aprotic organic solvent and a lithium salt dissolved in the organic solvent. The organic solvent includes a cyclic carbonate, an acyclic carbonate, and an acyclic fluorinated ether for improved low temperature and high voltage performance as well as enhanced thermostability. The ether group has a general formula of R.sub.1—O—[R.sub.3—O].sub.n—R.sub.2, where n=0 or 1, R.sub.1 and R.sub.2 are each straight-chain C1-C6 fluoroalkyl groups, and, when n=1, R.sub.3 is a methylene group or a polyethylene group.

A lithium secondary battery comprising a cathode, an anode, and an elastic polymer protective layer disposed between the cathode and the anode, and a working electrolyte in ionic communication with the anode and the cathode, wherein the elastic polymer protective layer comprises a high-elasticity polymer having a thickness from 2 nm to 200 μm, a lithium ion conductivity from 10.sup.−8 S/cm to 5×10.sup.−2 S/cm at room temperature, and a fully recoverable tensile elastic strain of at least 5% when measured without any additive or filler dispersed therein and wherein the high-elasticity polymer comprises a crosslinked polymer network of chains derived from a phosphazene compound and wherein the crosslinked polymer network of chains is impregnated with from 0% to 90% by weight of a liquid electrolyte.