The present invention provides a polymer which contains a repeating unit represented by formula (1).

##STR00001##

(In the formula, n represents an integer of 1 or more; R.sup.1 represents an optionally substituted monovalent aliphatic hydrocarbon group having from 1 to 60 carbon atoms, an optionally substituted monovalent aromatic hydrocarbon group having from 6 to 60 carbon atoms or an optionally substituted monovalent heterocyclic ring-containing group having from 2 to 60 carbon atoms; L represents a single bond, an optionally substituted divalent aliphatic hydrocarbon group having from 1 to 60 carbon atoms, an optionally substituted divalent aromatic hydrocarbon group having from 6 to 60 carbon atoms or an optionally substituted divalent heterocyclic ring-containing group having from 2 to 60 carbon atoms; and Ar represents an optionally substituted divalent aromatic hydrocarbon group having from 6 to 60 carbon atoms or an optionally substituted divalent heterocyclic ring-containing group having from 2 to 60 carbon atoms.)

The present invention provides a polymer which contains a repeating unit represented by formula (1).

##STR00001##

(In the formula, n represents an integer of 1 or more; R.sup.1 represents an optionally substituted monovalent aliphatic hydrocarbon group having from 1 to 60 carbon atoms, an optionally substituted monovalent aromatic hydrocarbon group having from 6 to 60 carbon atoms or an optionally substituted monovalent heterocyclic ring-containing group having from 2 to 60 carbon atoms; L represents a single bond, an optionally substituted divalent aliphatic hydrocarbon group having from 1 to 60 carbon atoms, an optionally substituted divalent aromatic hydrocarbon group having from 6 to 60 carbon atoms or an optionally substituted divalent heterocyclic ring-containing group having from 2 to 60 carbon atoms; and Ar represents an optionally substituted divalent aromatic hydrocarbon group having from 6 to 60 carbon atoms or an optionally substituted divalent heterocyclic ring-containing group having from 2 to 60 carbon atoms.)

The present invention comprises, in lithium composite oxide particles, an overlithiated oxide having a layered crystal structure and represented by chemical formula 1 below, and comprises a lithium manganese oxide represented by chemical formula 2 below outside the lithium composite oxide particles, wherein the overlithiated oxide included in the particles and the lithium manganese oxide included outside the particles have different Li/IM values. [Chemical formula 1] rLi.sub.2MnO.sub.3.(1-r)Li.sub.aNi.sub.xCo.sub.yMn.sub.zM1.sub.1-(x+y+z)O.sub.2 (wherein, in chemical formula 1, 0<r≤0.6, 0<a≤1, 0≤x≤1, 0≤y<1, 0≤z<1, and 0<x+y+z≤1, and M1 is at least any one selected from Na, K, Mg, Al, Fe, Cr, Y, Sn, Ti, B, P, Zr, Ru, Nb, W, Ba, Sr, La, Ga, Mg, Gd, Sin, Ca, Ce, Fe, Al, Ta, Mo, Se, Zn, Nb, Cu, in, S, B, and Bi) [Chemical formula 2] Li.sub.bMn.sub.pO.sub.q (wherein, in chemical formula 2, 0.1≤b/p≤2.5 and 0<q≤15).

The present invention comprises, in lithium composite oxide particles, an overlithiated oxide having a layered crystal structure and represented by chemical formula 1 below, and comprises a lithium manganese oxide represented by chemical formula 2 below outside the lithium composite oxide particles, wherein the overlithiated oxide included in the particles and the lithium manganese oxide included outside the particles have different Li/IM values. [Chemical formula 1] rLi.sub.2MnO.sub.3.(1-r)Li.sub.aNi.sub.xCo.sub.yMn.sub.zM1.sub.1-(x+y+z)O.sub.2 (wherein, in chemical formula 1, 0<r≤0.6, 0<a≤1, 0≤x≤1, 0≤y<1, 0≤z<1, and 0<x+y+z≤1, and M1 is at least any one selected from Na, K, Mg, Al, Fe, Cr, Y, Sn, Ti, B, P, Zr, Ru, Nb, W, Ba, Sr, La, Ga, Mg, Gd, Sin, Ca, Ce, Fe, Al, Ta, Mo, Se, Zn, Nb, Cu, in, S, B, and Bi) [Chemical formula 2] Li.sub.bMn.sub.pO.sub.q (wherein, in chemical formula 2, 0.1≤b/p≤2.5 and 0<q≤15).

A negative electrode active material for a secondary battery for achieving high initial efficiency and improved discharge capacity and capacity retention. The negative electrode active material for a secondary battery includes first silicon oxide powder particles doped with at least one of alkali metal or alkaline earth metal, and second silicon oxide powder particles, which are not doped, wherein the second silicon oxide powder particles are amorphous. A negative electrode and a secondary battery including the negative electrode active material are also disclosed.

A negative electrode active material for a secondary battery for achieving high initial efficiency and improved discharge capacity and capacity retention. The negative electrode active material for a secondary battery includes first silicon oxide powder particles doped with at least one of alkali metal or alkaline earth metal, and second silicon oxide powder particles, which are not doped, wherein the second silicon oxide powder particles are amorphous. A negative electrode and a secondary battery including the negative electrode active material are also disclosed.

Improved electrolytes for lithium-based cells can include a dual salt combination of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide or lithium bis(trifluoro-methanesulfonyl)imide, and a solvent that includes dimethyl carbonate, ethylmethyl carbonate and 5 to 25 volume percent of fluoroethylene carbonate. The improved electrolytes can include additives triethyl phosphate, ethoxy(pentafluoro)cyclotriphosphazene, 1,3-propane sultone, or mixtures thereof, and have small limited amounts of additional cosolvents and/or lithium-free organic additives. The improved electrolytes can be used to prepare lithium-based cells with silicon-based active materials as negative electrodes and nickel rich lithium metal oxides as positive electrodes. The lithium-based cells can achieve high energy, high power, fast charge and long cycle life along with good thermal stability.

Improved electrolytes for lithium-based cells can include a dual salt combination of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide or lithium bis(trifluoro-methanesulfonyl)imide, and a solvent that includes dimethyl carbonate, ethylmethyl carbonate and 5 to 25 volume percent of fluoroethylene carbonate. The improved electrolytes can include additives triethyl phosphate, ethoxy(pentafluoro)cyclotriphosphazene, 1,3-propane sultone, or mixtures thereof, and have small limited amounts of additional cosolvents and/or lithium-free organic additives. The improved electrolytes can be used to prepare lithium-based cells with silicon-based active materials as negative electrodes and nickel rich lithium metal oxides as positive electrodes. The lithium-based cells can achieve high energy, high power, fast charge and long cycle life along with good thermal stability.

A method of making anode active material including silicon, elemental sulfur and a polymer material for an electrochemical energy storage device, includes mixing together silicon particles, elemental sulfur, and at least one polymer to form a mixture; coating the mixture onto a copper current collector to form a coated copper current collector; and subjecting the coated copper current collector to a temperature treatment. An electrochemical energy storage device includes the anode active material, cathode and electrolyte.

A method of making anode active material including silicon, elemental sulfur and a polymer material for an electrochemical energy storage device, includes mixing together silicon particles, elemental sulfur, and at least one polymer to form a mixture; coating the mixture onto a copper current collector to form a coated copper current collector; and subjecting the coated copper current collector to a temperature treatment. An electrochemical energy storage device includes the anode active material, cathode and electrolyte.