Provided is a method for producing a negative electrode for an electric storage device, the method comprising the steps of preparing a negative electrode composition comprising a negative electrode active material that reversibly carries a sodium ion, metal sodium, and a liquid dispersion medium for dispersing them; allowing a negative electrode current collector to hold the negative electrode composition; evaporating at least part of the liquid dispersion medium from the negative electrode composition held by the negative electrode current collector, thereby giving a negative electrode precursor comprising the negative electrode active material, the metal sodium, and the negative electrode current collector; and bringing the negative electrode precursor into contact with an electrolyte having sodium ion conductivity, thereby doping the negative electrode active material with sodium eluted from the metal sodium.

According to one embodiment, a battery is provided. The battery includes one or more electrode stack. The one or more electrode stack includes an electrolyte layer, a first electrode layer, and a second electrode layer. The electrolyte layer includes an electrolyte and a carboxymethylcellulose sodium salt. The first electrode layer includes a first active material and a carboxymethylcellulose ammonium salt. The second electrode layer includes a second active material and a first binder soluble in an organic solvent. The first electrode layer is bound to a first surface of the electrolyte layer. The second electrode layer is bound to a second surface of the electrolyte layer on a reverse side to the first surface.

An electrolytic solution including a heteroelement-containing organic solvent at a mole ratio of not greater than 1.5 relative to a metal salt, the heteroelement-containing organic solvent containing a linear carbonate represented by general formula (1) below, the metal salt being a metal salt whose cation is an alkali metal, an alkaline earth metal, or aluminum and whose anion has a chemical structure represented by general formula (2) below.

R.sup.10OCOOR.sup.11  general formula (1)

(R.sup.21X.sup.21)(R.sup.22SO.sub.2)N  general formula (2)

An electrolytic solution including a heteroelement-containing organic solvent at a mole ratio of not greater than 1.5 relative to a metal salt, the heteroelement-containing organic solvent containing a linear carbonate represented by general formula (1) below, the metal salt being a metal salt whose cation is an alkali metal, an alkaline earth metal, or aluminum and whose anion has a chemical structure represented by general formula (2) below.

R.sup.10OCOOR.sup.11  general formula (1)

(R.sup.21X.sup.21)(R.sup.22SO.sub.2)N  general formula (2)

The present invention is intended to provide a gel-type solid electrolyte having flexibility while maintaining the advantages of an ionic liquid by effectively internalizing the ionic liquid into a porous metal oxide. To this end, the present invention provides the gel-type solid electrolyte which includes an ionic liquid in a porous metal oxide prepared from a silane compound represented by the following Chemical Formula 1:
Si(R.sub.1).sub.x(OR.sub.2).sub.y(CR.sub.3═CR.sub.4R.sub.5).sub.(4-x-y)  [Chemical Formula 1] in the Formula, R.sub.1 and R.sub.2 are alkyl groups with carbon numbers in the range of 1 to 3, which are independent from each other; R.sub.3, R.sub.4 and R.sub.5 are each independently hydrogen, a halogen element or an alkyl group having 1 to 5 carbon atoms; and x is an integer in the range of 0≦x≦3, y is an integer in the range of 1≦y≦4 and x+y is an integer in the range of 2≦x+y≦4.

The present invention is intended to provide a gel-type solid electrolyte having flexibility while maintaining the advantages of an ionic liquid by effectively internalizing the ionic liquid into a porous metal oxide. To this end, the present invention provides the gel-type solid electrolyte which includes an ionic liquid in a porous metal oxide prepared from a silane compound represented by the following Chemical Formula 1:
Si(R.sub.1).sub.x(OR.sub.2).sub.y(CR.sub.3═CR.sub.4R.sub.5).sub.(4-x-y)  [Chemical Formula 1] in the Formula, R.sub.1 and R.sub.2 are alkyl groups with carbon numbers in the range of 1 to 3, which are independent from each other; R.sub.3, R.sub.4 and R.sub.5 are each independently hydrogen, a halogen element or an alkyl group having 1 to 5 carbon atoms; and x is an integer in the range of 0≦x≦3, y is an integer in the range of 1≦y≦4 and x+y is an integer in the range of 2≦x+y≦4.

A solid-state electrolyte is presented that is a combined salt of an alkali metal or alkali earth metal closo-borate and alkali metal or alkali earth metal conductivity enhancing anion salt. The combined salt allows significantly higher conductivities in the solid state than the included alkali metal or alkali earth metal closo-borate. The combined salt can be prepared by mechanical combination or combination in solution. The salts can be used in solid-state electrochemical devices.

A solid-state electrolyte is presented that is a combined salt of an alkali metal or alkali earth metal closo-borate and alkali metal or alkali earth metal conductivity enhancing anion salt. The combined salt allows significantly higher conductivities in the solid state than the included alkali metal or alkali earth metal closo-borate. The combined salt can be prepared by mechanical combination or combination in solution. The salts can be used in solid-state electrochemical devices.

Provided is a lithium secondary battery having both visible light transparency and flexibility. A lithium secondary battery includes: a positive electrode film formed on a flexible transparent film substrate and capable of intercalating and deintercalating lithium ions; a transparent electrolyte having lithium ion conductivity; and a negative electrode film formed on a flexible transparent film substrate, the negative electrode film being a metal capable of forming an alloy with lithium or capable of intercalating and deintercalating lithium ions. When the positive electrode film contains a lithium source, the negative electrode film is made to have a thickness of 50 nm to 300 nm by using, as a negative electrode material, any of tin oxide, silicon oxide, titanium oxide, tungsten oxide, niobium oxide, molybdenum oxide, metal phosphide, metal sulfide, metal nitride, metal fluoride, or metal titanium composite oxide.

Provided is a lithium secondary battery having both visible light transparency and flexibility. A lithium secondary battery includes: a positive electrode film formed on a flexible transparent film substrate and capable of intercalating and deintercalating lithium ions; a transparent electrolyte having lithium ion conductivity; and a negative electrode film formed on a flexible transparent film substrate, the negative electrode film being a metal capable of forming an alloy with lithium or capable of intercalating and deintercalating lithium ions. When the positive electrode film contains a lithium source, the negative electrode film is made to have a thickness of 50 nm to 300 nm by using, as a negative electrode material, any of tin oxide, silicon oxide, titanium oxide, tungsten oxide, niobium oxide, molybdenum oxide, metal phosphide, metal sulfide, metal nitride, metal fluoride, or metal titanium composite oxide.