Patent Publication Number: US-2009233166-A1

Title: Lithium-ion battery with medium and small capacity and high output

Description:
FIELD OF THE INVENTION 
     The invention relates to a lithium-ion battery, especially to a lithium-ion battery with medium and small capacity. 
     BACKGROUND OF THE INVENTION 
     As to the lithium-ion battery with medium and small capacity (capacity of 1-3 Ah), lithium-ion batteries developed before almost are volumetric type battery whose discharging current and output power are usually very low, and discharging magnification is usually lower than 5 C. 
     However, in the field which needs high-current to charge and discharge, such as the application fields of electric tool, electric toy etc., nickel-hydrogen battery and nickel-cadmium battery occupied the market for long-term. Recently, the European Union has forbidden all products containing poison material of lead, mercury, cadmium and so on to enter the European market, so the nickel-cadmium battery with market share of above 90% will be limited outside the European market. Thus, needs a kind of lithium-ion battery with medium and small capacity which can have higher discharging current and output power, such as discharging magnification of high than 5 C or much higher, to meet the requires. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to overcome the shortages of the prior art, and provide a lithium-ion battery with medium and small capacity and high output. 
     In order to realize the above said object, the invention provide a lithium-ion battery with medium and small capacity and high output, comprising a shell, a cell core and electrolyte located in the shell; the said cell core obtained by winding anode sheets, cathode sheets and separators between the anode sheets and cathode sheets, the said anode and cathode sheets coated with active material; the said anode active material including LiMn 2 O 4 , especially still including LiCoO 2  and/or LiNiCoO 2;  and the said electrolyte having the conductivity of 11-20 ms/cm; the length of the said anode sheets and cathode sheets is 700-2400 mm, and the thickness is 65-135 μm. 
     The advantages of the invention are below:
         1) It can increase the energy density of the battery without decreasing the power density of the battery by choosing proper anode active material in the invention.   2) The anode and cathode sheets are long sheets with the length and thickness not only fit for lowering the current in unit area, but also fit for lithium-ion to embed in and off to increase input and output capability of the battery with high current.   3) The invention uses the electrolyte with high conductivity of 11-20 ms/cm, thus the transmission of lithium-ion will be easy, and it will further improve the input and output capability of the battery with high current.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a schematic view of the structure of the cell core in the lithium-ion battery; 
         FIG. 2(   a ) is a schematic plan view of the anode and cathode sheets in the lithium-ion battery; 
         FIG. 2(   b ) is a side view of the anode and cathode sheets in the lithium-ion battery; 
         FIG. 3  is a curve of the discharging magnification of the lithium-ion battery made by the invention. 
     
    
    
     DETAILED DESCRIPTION 
     A lithium-ion battery usually comprises a shell, a cell core and electrolyte located in the shell.  FIG. 1  schematicaly shows the cell core  10  which is obtained by winding anode sheets  11 , cathode sheets  12  and separators  13  between the anode sheets and cathode sheets. The cell core  10  is located in the shell (not shown), and fill up the electrolyte inside in the shell of the battery. The anode and cathode sheets  11  and  12  are as shown in  FIG. 2(   a ) and  FIG. 2(   b ), including coated areas  14  and uncoated areas  15 . The coated areas  14  of anode sheets is coated with anode active material, while the coated areas  14  of cathode sheets is coated with cathode active material, and the coated areas  14  are usually coated with materials of conduction substance and adhesive substance and so on. The uncoated areas  15  of the anode and cathode sheets  11  and  12  use to connect the electrode ear ( )(not shown). The above said contents are known by the skilled persons of this field. 
     In the lithium-ion battery with medium and small capacity and high output of the invention, the anode active material includes LiMn 2 O 4 ; it is better to include LiCoO 2  and/or LiNiCoO 2 . In an example, the anode active material only includes LiMn 2 O 4 . In another example, the anode active material is a mixture of LiMn 2 O 4  and LiCoO 2 . In another example, the anode active material is a mixture of LiMn 2 O 4  and LiNiCoO 2 . In another example, the anode active material is a mixture of LiMn 2 O 4 , LiCoO 2 , and LiNiCoO 2 . 
     When the anode active material includes include LiCoO 2  and/or LiNiCoO 2 , LiCoO 2  or LiNiCoO 2  or their mixture would be 10%-29% of the gross weight of the anode active material, and correspondingly LiMn 2 O 4  is 71%-90% of the gross weight of the anode active material. The proportion between LiCoO 2  and LiNiCoO 2  can be chose randomly. In some examples, LiCoO 2  or LiNiCoO 2  or their mixture is 10%, 29% of the gross weight of the anode active material, and correspondingly LiMn 2 O 4  is 90%, 71% of the gross weight of the anode active material. 
     In the invention, the conductivity of the electrolyte is 11-20 ms/cm, preferred 11-15 ms/cm. In some examples, the conductivity of the electrolyte can choose 11 ms/cm, 12 ms/cm, 15 ms/cm, or 20 ms/cm. 
     In the invention, the length range of the anode sheets  11  and cathode sheets is 700-2400 mm, such as 700 mm, 1500 mm or 2000 mm; while the thickness (including coated material on the anode and cathode sheets) range is 65-135 μm, such as 65 μm, 85 μm, 100 μm, 120 μm. 
     Two examples of the lithium-ion battery of the invention will be illustratively described below. 
     EXAMPLE 1  
     Use anode active material of LiMn 2 O 4  and anode sheets with length of 750-800 mm and thickness of 125-135 μm, cathode sheets with length of 800-850 mm and thickness of 75-85 μm, and the electrolyte with conductivity of 11 -15 ms/cm to make the lithium-ion battery with capacity of 1.1-1.2 Ah. 
     EXAMPLE 2  
     Use anode active material made by mixing certain proportion of LiMn 2 O 4  and LiNiCoO 2 , wherein LiMn 2 O 4  is 90% by weight and LiNiCoO 2  is 10% by weight, and anode sheets with length of 1500-1600 mm and thickness of 125-135 μm, cathode sheets with length of 1550-1650 mm and thickness of 75-85 μm, and the electrolyte with conductivity of 11-15 ms/cm to make the lithium-ion battery with capacity of 2.2-2.5 Ah. 
     Tests show that the lithium-ion battery made by the invention can have excellent discharging property, and excellent quick charging property, thus fitting for usage mode of the electric tool to quickly charge and discharge. Discharging property and charging property are shown in the tables below. 
     
       
         
           
               
               
               
             
               
                   
               
               
                 Magnification of 
                 Time of 
                 Capacity of 
               
               
                 discharging 
                 discharging 
                 discharging 
               
               
                   
               
             
            
               
                  5 C 
                 11.6 min  
                 97% 
               
               
                 10 C 
                 5.5 min 
                 92% 
               
               
                 20 C 
                 2.6 min 
                 88% 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
               
               
                 Magnification of 
                 Time of 
                 Capacity of 
               
               
                 charging 
                 charging 
                 charging 
               
               
                   
               
             
            
               
                 2 C 
                 27 min 
                 90% 
               
               
                 3 C 
                 17 min 
                 85% 
               
               
                 5 C 
                  6 min 
                 50% 
               
               
                   
               
            
           
         
       
     
       FIG. 3  is a curve of the discharging magnification of the lithium-ion battery made by the invention. It shows the lithium-ion battery with medium and small capacity and high output made by the invention has excellent discharging ability with high current, thus satisfying the operation of electric tool and so on.